TRADE union membership could be reduced to “near zero” within 15 years by the Tories’ anti-union laws, Prospect’s general secretary has warned.

The professional union’s leader Mike Clancy gave his dire diagnosis of the Trade Union Bill at a sparsely attended Unions 21 fringe meeting at Tory conference on Tuesday night.

Mr Clancy said the Bill could see the Tories complete their “historic mission” to crush the labour movement.

He claimed public opinion was behind the Tories’ Bill “in relation to unrepresentative strike action on stagnant mandates from some time ago.”

But the union leader challenged around 20 Conservative members to consider the long-term consequences of the Bill.

He asked: “What’s the end point of public policy in terms of trade union membership? Do you want zero?

“Because if you don’t want zero, there must be a figure in your mind that you think public policy should stimulate for the good of the economy and working people.

“If we carry on down the route with some of the things that are in the Trade Union Reform Bill, in 10-15 years we’ll get near to zero.

“You might think that’s a historic mission complete, but we are at a watershed moment in terms of the fabric of unions and their ability to contribute to prosperity.”

One Tory member responded by taking a pop at trade union facility time, insisting it should be paid for by unions.

But one Conservative councillor admitted: “I’m a Conservative councillor and I do get time off work to be a Conservative councillor and don’t get paid by the Conservative Party to do that. I’ll just make that point.”