DAVID CAMERON climbed down on controversial trade union reforms to secure union support for the EU referendum Remain campaign in an echo of the "cash for questions" scandal, a leading Eurosceptic has claimed.

Bernard Jenkin claimed No 10 instructed ministers to offer concessions on the Trade Union Bill over members opting in to political funds after discussions with union representatives in order to get their support for Remain.

The Conservative MP said it amounted to "the sale of Government policy for cash and political favours" and put the Government at the "rotten heart" of the European Union.

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Mr Jenkin said the Prime Minister should instruct his adviser on ministerial interests to investigate whether discussions between ministers, officials and trade union representatives or Labour about the Bill breached the Ministerial Code.

Asking an urgent question in the Commons, he said: "It has been confirmed to me through more than two independent sources that No 10 instructed these concessions to be made after the discussions with trade union representatives.

"This being true would amount to the sale of Government policy for cash and political favours."

He went on: "This stinks, this reeks of the same as cash for questions.

"This shows this Government really is at the rotten heart of the European Union."

MPs approved concessions to the Trade Union Bill on Wednesday following a series of defeats over the plans in the House of Lords.

One of the compromises included a climbdown on attempts to force all trade union members to have to opt-in to paying a political levy.

The opt-in will now only apply to new union members and not existing members, as originally planned.

But Mr Jenkin said the compromises were "wholly unexpected" and claimed they were linked to a £1.7 million donation unions may make from their political funds to the Labour Remain campaign - Labour In For Britain.

Business Minister Nick Boles insisted there was no breach of the ministerial code and that the reforms still fulfilled Tory manifesto commitments to clamp down on the unions.

But Mr Jenkin invited Labour and Mr Boles to consider alternative but similar scenarios.

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He said: "Lest there be any doubt about the impropriety of this deal, Her Majesty's Opposition should just ask themselves this question - what would they be saying if this Government had altered a Bill in order to give extra money to the Conservative Party or to (the) Conservatives' Remain campaign - Conservatives In.

"And you (Mr Boles) should ask yourself this question - what would have been the reaction if a Labour government had changed a Bill in order to favour the Labour Party's ability to support the Government on some controversial policy and to give it money?"

Earlier, Mr Boles insisted there was no wrongdoing and that the opt-in process had been made more transparent.

"The Cabinet Office has advised me that there is no breach of the ministerial code and nothing for the Prime Minster's adviser on ministerial interests to investigate," the minister said.

"The Trade Union Bill is now in ping pong and, as is customary at such times, ministers have held regular discussions with shadow ministers to discuss possible compromises that would secure passage of the Bill and delivery of the commitments made in the Conservative Party's manifesto.

"On the basis of the amendments passed by this House yesterday evening I can reassure you that we are well on the way to securing all of our manifesto commitments - ballot thresholds for strikes, reforms to the role of the certification officer, a tightening up of rules around facility time, action to stop intimidation of non-striking workers, and the introduction of a transparent opt-in process for union members' contributions to political funds."

Mr Boles also pointed out that many leading unions declared their support for Remain long before the concessions were offered.

He said: "You will not be surprised to learn that I hold regular meetings with trade union leaders and the general secretary of the TUC, not just in relation to the Bill but also in relation to other responsibilities of mine.

"Trade union support for the campaign to remain in the European Union is not new and should not come as a surprise to anyone.

"The TUC declared its support for the campaign in February, the GMB union did the same on February 22, Unite on March 14, and Unison on April 13."

Mr Boles, in his reply to Mr Jenkin, said the amendment over the opt-in for trade union members was proposed by crossbench peer Lord Burns - not by Labour peers.

He said major opposition from the Lords, including from prominent Tories, led to the Government shifting its position.

Mr Boles also told Mr Jenkin: "You suggested it is inappropriate for Government to do anything for private interests, in terms of making changes to legislation to further private interests - and of course you're right."

But Mr Boles said it is "simply not right" to categorise the Government's official policy of Britain remaining in the EU as a private interest.

He told Mr Jenkin: "You disagree, honourably and valiantly. But it is not a private interest, it is Government policy."

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