Postal workers are to stage a fresh 24-hour strike in a bitter row over pay and jobs.
The Communication Workers Union said up to 130,000 of its members would walk out from 7pm on Thursday, following an earlier stoppage last month.
The union has written to Royal Mail chairman Allan Leighton calling for fresh talks and outlining a deal it believed could break the deadlocked row.
It has rejected a 2.5% pay offer and warned that the Royal Mail's modernisation plans will lead to the loss of 40,000 jobs.
Union representatives met with Royal Mail on Wednesday in a bid to begin fresh talks.
But the union afterwards said: "Disappointingly, Royal Mail simply concentrated on reiterating their previous offer that the workforce has already overwhelmingly rejected."
And at midday on Friday, postal workers plan to arrive at the Royal Mail's head office in London on a red open top bus.
They will hand over an oversized open letter addressed to Mr Leighton, calling for a return to negotiations.
The Royal Mail has said it was "deeply disappointed" that another strike had been called, warning of further disruption for customers.
A spokesman said previously: "Further strike action will achieve nothing. The union is saying nothing new and is simply ignoring the challenge confronting everyone in Royal Mail which is the absolute need to modernise - as all our major rivals have already done."
