Trade unions are to demand changes in the law to make it easier to go on strike as the Labour party increasingly depends on them for its financial survival.

The demand will be put to a crucial gathering of Labour policymakers this month. The unions argue current regulations favour employers and they must “jump through hoops” before they can take legal industrial action. Big organisations such as the GMB and Unite say the current rules about balloting for strikes are full of “legalese”, making them vulnerable to challenges by the courts.