It is “fanciful” to suggest voters do not know the UK is a member of the European Union, Tory chairman Grant Shapps said as he rejected calls to amend legislation enshrining the pledge for a vote on whether to sever ties with Brussels.
The elections watchdog suggested Tory backbencher James Wharton's bill should be altered to make it clear the country was already part of the 28-member group.
But Mr Shapps said there was no reason to delay progress of the legislation, which returns to the Commons on Friday, and urged Labour and Liberal Democrat MPs to back the bill.
Under current plans the legislation will mean voters being asked in 2017: "Do you think that the United Kingdom should be a member of the European Union?"
But the Electoral Commission has suggested asking "should the United Kingdom remain a member of the European Union?" because some voters apparently do not know their country already is part of the EU.
It added that a more neutral alternative would be "should the United Kingdom remain a member of the European Union or leave the European Union?" - though that would mean voters would be asked to vote to remain or leave instead of answering yes or no.
But Mr Shapps rejected the call for a change in wording, which could jeopardise the private member's bill's progress through Parliament.
He said: "The idea that we don't know we are in the EU is rather fanciful. The question is worded in a very straightforward manner. There is no reason to delay."
Mr Wharton's European Union (Referendum) Bill has so far survived its initial Commons stages unscathed and is being returned to MPs after committee consideration on Friday.
But Labour MP and former Foreign Affairs Select Committee chairman Mike Gapes has now proposed more than 50 different amendments for the private member's bill's report stage.
Earlier amendments by former shadow Europe minister Emma Reynolds relating to Gibraltar and a bid by would-be Conservative leadership contender Adam Afriyie to bring forward a referendum to next year are also still on the table.
The raft of amendments increases the prospect of the legislation running out of parliamentary time and not becoming law despite the coordinated efforts of almost all Conservative MPs.
Legislation brought forward by individual backbenchers can only be discussed on Friday sittings of the Commons and only six are left on the Parliamentary calendar in the current session.
Mr Shapps urged Labour and Liberal Democrat MPs to "hear the nation" and lend their support to the bill.
He said: "It is a big moment on Friday. James Wharton, who has been heroically leading this with full Conservative Party support, has the will of the nation behind him.
"People think it's time for an in/out referendum. It is now important for Labour and the Lib Dems to show that they hear the nation."
He insisted the 2017 timetable was necessary to allow the UK to renegotiate its relationship with the EU ahead of the in/out vote.
"We want to have the opportunity to negotiate the best possible 'in' terms first," he said.