The prisoners, all members of the Confederation of Public Employees Unions (KESK), face trial on November 19 and 20.

In an open letter to Mehmet Yigit Alpogan, Mr Barber said that the Turkish authorities were in "serious" breach of international labour laws and demanded the immediate release of all the prisoners.

"The TUC shares the view of the international trade union movement in calling for the imprisoned trade unionists to be freed and all other threats of imprisonment against independent trade unionists for their legitimate activities to be lifted," he demanded.

Mr Barber also warned the Turkish government that its continued repression of trade unions would further spoil the country's chances of joining the EU.

The letter, which has also been sent to the British Foreign Secretary and Minister for Europe, is part of a wider solidarity campaign by the International Trade Union Confederation (ITUC) and its affiliates to secure the release of the KESK members.

On May 28, the Turkish Gendarmerie - part of the Turkish armed forces - raided KESK headquarters in Ankara, its branch offices in Ezmir and Van, and even stormed the houses and workplaces of some of the senior members.

They targeted KESK women secretary Songül Morsümbül's office and confiscated all official documents, including her laptop and 18 CDs, as criminal evidence.

Around 35 KESK members were arrested, 22 of which remain in jail.

The union has 10 other members still in prison from an earlier wave of arrests.

KESK believes that the arrests were in connection with the union's recent struggle for a national collective agreement and its successful demonstrations against the impact of the economic crisis and the "systematic" repression of trade unionists.

The government has reportedly claimed that it was part of a bigger operation to crack down on the Kurdish militant group PKK, which the authorities consider to be a terrorist organisation.

KESK has vowed to "continue our struggle until all of our members are released.

"If these attacks and violations are not prevented in Turkey, then the trade union movement and the struggle for democracy, freedom, equality and woman rights will be seriously harmed."