Theresa May has got to come clean about the cost of Brexit

Once again, the national interest is being subordinated to the higher cause of holding the Conservative Party together

Theresa May is putting party politics before national interest (AFP/Getty)

We know what the Prime Minister is up to. She wants to keep quiet about the size of the exit fee she is offering to the European Union until after Monday’s lunch with Jean-Claude Juncker, the Europan Commission President, and Michel Barnier, the EU negotiator. Indeed, she does not want her own MPs to know the sum until after the European Council on 14 and 15 December, at which she hopes to secure agreement to move to the next phase of Brexit talks.

Once again, the national interest is being subordinated to the higher cause of holding the Conservative Party together – the sort of thing that prompted David Cameron to get us into the mess we are now in.

It is a small consolation, therefore, that the official opposition, led on this question by Sir Keir Starmer, the Shadow Brexit Secretary, is holding the Government to account. Labour is tabling an amendment to the EU (Withdrawal) Bill on Wednesday that would require any financial settlement to be assessed by the Office for Budget Responsibility and the National Audit Office.

Of course, The Independent regards the prospect of a settlement amounting to between £45bn and £55bn as reasonable in principle. The reasons Conservative Eurosceptics might find it hard to accept are obvious. One is that they ran a referendum campaign on the assumption that leaving the EU would save the British people vast sums that could be diverted to the health service or other popular causes. The divorce bill gives the opposite impression.

This impression is reinforced by the way the sum, made up of several separate items, is rolled up into one very big number. In fact, of the £45bn-£55bn, about £20bn represents the continuation of our net contributions for the two years of a transition period, in which we would continue to be an EU member in all but name (and influence). The rest, Ms May insists, is similarly money that we owe in any case as a consequence of our membership.

If so, there can be no objection to its being scrutinised to confirm it – or to giving Parliament the chance to approve or reject it in a vote. As Lord Heseltine, the former Deputy Prime Minister, told The Independent, “What would a Conservative opposition do if a Labour Party proposed to spend £30bn, £40bn or £50bn without telling Parliament what it was doing with it?”

Nor should Ms May’s desire to avoid a confrontation with the Eurosceptic wing of her own party be a deciding factor. If she secures progress to the next stage of the Brexit talks in the next two weeks, that would be something of a negotiating triumph. Having secured that objective with remarkably little fuss from the cut-and-runners in her own party, however, she has to accept that the final figure will become known before the Brexit deal is sealed, if it ever is.

She should, therefore, accept Labour’s amendment and commit to being open with Parliament as the final sums are calculated.

Bad though Brexit may be for the nation, if it cannot be postponed or reversed it is important that we obtain the best deal possible. That means seeking the greatest possible degree of consensus, in Parliament and beyond. That in turns means that the Government must be open with the British people about the cost of Brexit.