Lobbying reforms have caused a political storm in Westminster, with Labour accusing the Prime Minister of undermining the party's trade union support.
Speaking to Daybreak, TUC Assistant General Secretary Paul Novak said: "The Government is using this in a cheap cynical way to score points against the trade unions and the six and half a million people that we represent.
"We think that the trade union money that is in politics, the resources that we put into politics", he added. "That's the most honest money in politics."
The Government will bring forward a bill to introduce a statutory register of lobbyists before Parliament's summer recess in July.
The hastily announced Government bill to create a statutory register of lobbyists is a highly politicised piece of legislation.