LONDON - Postal disruption looked set to widen on Tuesday, after talks broke down and union officials warned of fresh strikes.

Up to 130,000 postal staff remained on picket lines in the second day of a 48-hour walk-out in a dispute over pay, jobs and working conditions.

The Communication Workers Union (CWU) has been in talks with Royal Mail bosses for eight days, but no agreement has emerged.

The union said a series of fresh strikes would start on Monday unless the deadlocked dispute -- which has seen a previous 48-hour strike -- is resolved.

The proposed series of new 24-hour strikes by different departments is designed to disrupt services while ensuring workers lose just one day's pay.

TUC General Secretary Brendan Barber, who chaired the negotiations, said: "I am very disappointed that this phase of intensive talks has not resolved the dispute when real progress has been made and we have been edging towards an agreement."

He said he would keep in close touch with both parties to "continue to seek to find a way forward".

Prime Minister Gordon Brown said in the House of Commons on Monday that the government would not intervene in the dispute, but would not "stand idly by".

But Adam Crozier, chief executive of Royal Mail, said there was no requirement for government intervention.

Speaking on BBC Radio Four on Tuesday, he added: "I think everyone would like it sorted; we'd particularly like it sorted for our customers, we'd like it sorted for our people who will have lost hundreds of pounds needlessly.

Crozier said the "vast majority" of employees were beginning to return to work and that the company was able to move around 60 percent of mail.

The firm's competitors, he noted, were 40 percent more efficient but paid their workers 25 percent less.

Postal economist Ian Senior said the strikes would severely damage Royal Mail.

Ever since postal regulator Postcomm was established, it had attempted to "interfere, micro-manage" the postal service, holding prices down well below competitors in Europe, he said.

"Royal Mail has been moved from a position of being reasonably profitable, now to a position of being zero profitable," he said.

"And I suspect after this strike it will be a loss-maker."

He said the action would serve to "hasten the long-term decline of the letter as a form of communication", a process started by the advent of email.