The Communication Workers Union (CWU) has announced that it plans to launch legal action to stop Royal Mail using agency staff to clear the backlog caused by the postal strikes.
Royal Mail has denied that its move to hire 30,000 temporary workers breaches employment law. Talks aimed at averting a three more days of strikes this week will resume at the Trades Union Congress later today.
The two sides held seven hours of discussions before adjourning on Monday night. The talks' host, TUC general secretary Brendan Barber, described the session as "useful" and said he was hopeful progress could be made.
Up to 120,000 CWU members will stage three 24-hour strikes from Thursday if no agreement is reached.
The union's deputy general secretary, Dave Ward, said the dispute was "fundamentally" about jobs and working conditions. But he added that Royal Mail's £10bn pension deficit needed to be deal with urgently.
He said: There's no prospect of us building a successful future for the Royal Mail and for the workforce unless the Government actually deal with that issue."
He added: "We will deal with the issues around the industrial side of the Royal Mail but there are things that the Government have to deal with. Unless we fund a solution to the pensions deficit very quickly then this company has no prospect of building a successful future."
Royal Mail expects the backlog to have fallen from 30 million to five million items since last week. The CWU had claimed 100 million items remained undelivered on Saturday.
