Parliament must still vote on a bill to allow the UK to leave the European Union, leading lawyers have said.
Geoffrey Robertson QC, who founded the Doughty Street Chambers, said the act which set up the referendum said "nothing" about its impact, meaning it was "purely advisory".
A new bill to repeal the 1972 European Communities Act that took Britain into the EU must now be passed by parliament, he said, adding that MPs might not be able to vote until November when the economic effects of Brexit will be clearer.
"Under our constitution, speaking as a constitutional lawyer, sovereignty rests in what we call the Queen in parliament," he told The Independent.
"It's the right of MPs alone to make or break laws, and the peers to block them. So there's no force whatsoever in the referendum result. It's entirely for MPs to decide.
"The 1972 communities act ... is still good law and remains so until repealed. In November, Prime Minister [Boris] Johnson will have to introduce into parliament the European communities repeal bill," Mr Robertson said.
"MPs are entitled to vote against it and are bound to vote against it, if they think it's in Britain's best interest [to vote that way]. It's not over yet.
"MPs will have to do their duty to vote according to conscience and vote for what's best for Britain. It's a matter for their consciences. They have got to behave courageously and conscientiously.
6 ways Britain leaving the EU will affect you
6 ways Britain leaving the EU will affect you
1/6 More expensive foreign holidays
The first practical effect of a vote to Leave is that the pound will be worth less abroad, meaning foreign holidays will cost us more
2/6 No immediate change in immigration status
The Prime Minister will have to address other immediate concerns. He is likely to reassure nationals of other EU countries living in the UK that their status is unchanged. That is what the Leave campaign has said, so, even after the Brexit negotiations are complete, those who are already in the UK would be allowed to stay
3/6 Higher inflation
A lower pound means that imports would become more expensive. This is likely to mean the return of inflation – a phenomenon with which many of us are unfamiliar because prices have been stable for so long, rising at no more than about 2 per cent a year. The effect may probably not be particularly noticeable in the first few months. At first price rises would be confined to imported goods – food and clothes being the most obvious – but inflation has a tendency to spread and to gain its own momentum
4/6 Interest rates might rise
The trouble with inflation is that the Bank of England has a legal obligation to keep it as close to 2 per cent a year as possible. If a fall in the pound threatens to push prices up faster than this, the Bank will raise interest rates. This acts against inflation in three ways. First, it makes the pound more attractive, because deposits in pounds will earn higher interest. Second, it reduces demand by putting up the cost of borrowing, and especially by taking larger mortgage payments out of the economy. Third, it makes it more expensive for businesses to borrow to expand output
5/6 Did somebody say recession?
Mr Carney, the Treasury and a range of international economists have warned about this. Many Leave voters appear not to have believed them, or to think that they are exaggerating small, long-term effects. But there is no doubt that the Leave vote is a negative shock to the economy. This is because it changes expectations about the economy’s future performance. Even though Britain is not actually be leaving the EU for at least two years, companies and investors will start to move money out of Britain, or to scale back plans for expansion, because they are less confident about what would happen after 2018
6/6 And we wouldn’t even get our money back
All this will be happening while the Prime Minister, whoever he or she is, is negotiating the terms of our future access to the EU single market. In the meantime, our trade with the EU would be unaffected, except that companies elsewhere in the EU may be less interested in buying from us or selling to us, expecting tariff barriers to go up in two years’ time. Whoever the Chancellor is, he or she may feel the need to bring in a new Budget
"Democracy in Britain doesn't mean majority rule. It's not the tyranny of the majority or the tyranny of the mob ... it's the representatives of the people, not the people themselves, who vote for them."
Mr Robertson said there had been "a lot of stupid statements" suggesting Britain could simply send a note to the EU to trigger "Article 50" of the Lisbon Treaty, which lays out the process under which states can leave. The article itself says a state can only leave in accordance with "its own constitutional requirements".
"Our most fundamental constitutional requirement is that the decision must be taken by parliament. It will require a bill," he said.
"In November, the situation may have totally changed. According to polls, a million vote leavers appear to have changed their mind, that could be five million by the November."
In a letter to The Times, another leading QC, Charles Flint, of Blackstone Chambers, also stressed that British law required MPs to vote before Brexit could happen.
"Under the European Union Act 2011 ... a change to the treaty on European Union, agreed between member states, would have required approval both by referendum and by act of parliament," he said.
The Lisbon Treaty was the first agreement that laid out how member states could leave the EU.
Article 50 of the treaty says:
1. Any Member State may decide to withdraw from the Union in accordance with its own constitutional requirements.
2. A Member State which decides to withdraw shall notify the European Council of its intention. In the light of the guidelines provided by the European Council, the Union shall negotiate and conclude an agreement with that State, setting out the arrangements for its withdrawal, taking account of the framework for its future relationship with the Union. That agreement shall be negotiated in accordance with Article 218(3) of the Treaty on the Functioning of the European Union. It shall be concluded on behalf of the Union by the Council, acting by a qualified majority, after obtaining the consent of the European Parliament.
3. The Treaties shall cease to apply to the State in question from the date of entry into force of the withdrawal agreement or, failing that, two years after the notification referred to in paragraph 2, unless the European Council, in agreement with the Member State concerned, unanimously decides to extend this period.
4. For the purposes of paragraphs 2 and 3, the member of the European Council or of the Council representing the withdrawing Member State shall not participate in the discussions of the European Council or Council or in decisions concerning it.
A qualified majority shall be defined in accordance with Article 238(3)(b) of the Treaty on the Functioning of the European Union.
5. If a State which has withdrawn from the Union asks to rejoin, its request shall be subject to the procedure referred to in Article 49.