Vince Cable was subject to heckling by trade union activists after warning there could be tougher laws on strikes.

The Business Secretary was booed and shouted at as he spoke at the annual conference of the GMB union in Brighton.

As Cable cited damage to the economy that strikes could pose, delegates held up a banner as he spoke, which read: “Vince Cable not welcome – Stop Attacking Workers’ Rights.”

Cable warned that if unions persist in co-ordinated strike action, “the pressure on us to act [by changing the law] will ratchet up”.

He added: “If we go into a cycle of destructive strikes, we would have to think again [on strike laws].”

It’s ironic to note that the warning comes from a Lib Dem who was previously viewed by Conservatives as a potential block to a change in law.

Prime Minister David Cameron’s spokesman told reporters there were no current proposals to change the law on the right to strike, but made clear that ministers were ready to review the position if there was a wave of “irresponsible” disputes.

GMB general secretary Paul Kenny said Cable’s comments were an “insult to working people” while RMT leader Bob Crow claimed they were “calculated to be both provocative and insulting”.

Union leaders have warned 750,000 teachers, lecturers, civil servants and other public sector workers could take co-ordinated strike action on June 30 in the biggest outbreak of industrial unrest for years.

Cable told the conference: “The usual suspects will call for general strikes and widespread disruption.

“This will excite the usual media comments about a summer or an autumn of discontent, and another group of the usual suspects will exploit the situation to call for the tightening of strike law.

“We are undoubtedly entering a difficult period. Cool heads will be required all round.

“Despite occasional blips, I know that strike levels remain historically low, especially in the private sector.

“On that basis, and assuming this pattern continues, the case for changing strike law is not compelling.

“However, should the position change, and should strikes impose serious damage to our economic and social fabric, the pressure on us to act would ratchet up.

“That is something which both you, and certainly I, would wish to avoid.”

Cable’s aides have been scrambling to emphasise that the Government feels there is no case for changing strike laws at the moment and that unions have acted responsibly so far.

But he is keen to draw a distinction between himself and what he calls the “usual suspects” who are “exploiting” the situation.

Mayor of London Boris Johnson and employers’ organisation the Confederation of British Industry (CBI) have already called for tougher trade union laws.

Johnson wants laws to prevent a strike taking place unless at least half of the union members in a workplace take part in a ballot.

He has criticised the government as “lily-livered” for not taking firmer action.

The CBI has called for a minimum of 40 per cent of union members balloted to be in favour of a strike before it can take place.

However, Cable is said to favour changes in the law that would ensure unions have to provide a minimum service level during a strike.