David Cameron orders inquiry into trade union tactics

A Unite placard at the Grangemouth oil refinery. Photograph: Murdo Macleod for the Guardian

David Cameron has ordered an inquiry into the tactics of trade unionsafter a bitter industrial dispute almost led to the closure of the Grangemouth oil refinery in Scotland.

Downing Street said the wide-ranging review, headed by Bruce Carr QC, would investigate allegations of the use of so-called leverage tactics by the unions, as well as the impact of such disputes on critical national infrastructure.

However, in a sign of renewed coalition tensions, the Liberal Democrat business secretary, Vince Cable, made clear he had only agreed to the inquiry on the basis that it would also examine the practices of employers, such as the blacklisting of workers.

The Unite union dismissed the review as a Tory election stunt and said no trade union would be prepared to collaborate with it.

There have been claims that Unite sought to intimidate executives from Ineos, the refinery's owners, including sending demonstrators to protest outside their homes and at premises associated with the Ineos chairman, Jim Ratcliffe.

In recent weeks the prime minister has repeatedly attacked the union in the Commons, challenging the Labour leader, Ed Miliband, to hold an inquiry into claims of vote-rigging in the Falkirk constituency party in an attempt to secure the selection of Unite's favoured candidate for parliament.

Unite's general secretary, Len McCluskey, has denied any intimidation or bullying on the part of the union, insisting that it acted within the law.

Carr will consider whether existing laws are sufficient to prevent what government sources described as "inappropriate or intimidatory actions" in trade disputes, as well as the response of the police to complaints.

He will look at the underlying causes of industrial relations difficulties, the potential impact on the UK's critical national infrastructure and the consequences for investor confidence in key sectors.

The review will make recommendations on the respective roles of government, employers and employee representatives in ensuring effective workforce relationships.