IAIN Duncan Smith, the leading Brexiteer, has accused David Cameron of ditching a proposed Sovereignty Bill in an attempt to improve his chances of winning the referendum on Britain's EU membership.

The former Work and Pensions Secretary was responding to suggestions the legislation, which was floated by the Prime Minister during his EU renegotiation as a constitutional safeguard, would not feature in today’s Queen's Speech being delivered at the State Opening of the UK Parliament.

Mr Duncan Smith said that, if confirmed, the absence of a bill asserting the UK's sovereignty would be the latest in a string of climbdowns aimed at keeping Britain in the EU.

"Many Conservatives have become increasingly concerned that in the Government's helter-skelter pursuit of the referendum, they have been jettisoning or watering down key elements of their legislative programme," said the Scot.

“Whether it is the Trade Union Bill or the BBC Charter proposals, it seems nothing must stand in the way of winning the referendum.

"Yet to compound that, now it appears the much-vaunted Sovereignty Bill, key to the argument that the PM had secured a reform of the EU, has been tossed aside as well.”

The Essex MP added: "The fear in Government must be that, as no-one in Britain buys the idea that the EU has been reformed, the Sovereignty Bill would draw the public's attention back to that failure. After all if the EU Court of Justice is supreme and can strike down our laws, the British people would have just laughed at the idea Britain can be sovereign unless we leave the EU."

As early as the 2010 Queen's Speech, the then coalition government said it would examine the case for a UK Sovereignty Bill to make clear that ultimate authority rested in Britain and not with the European Court of Justice in Luxembourg.

The idea was revived earlier this year as Mr Cameron sought to win over wavering "big beasts" like Boris Johnson and Michael Gove, who eventually opted to campaign for Britain to leave the EU.

While never publicly promising a Bill, the Prime Minister told MPs in February, in response to a question from Mr Johnson, that he would take action to "put beyond doubt that this House is sovereign".