The last-minute talks come as 120,000 workers are set to walk out over three-day strikes from Thursday this week.

Speaking on BBC1's Andrew Marr Show yesterday, Crozier said "I hope common sense will prevail".

CWU general secretary Billy Hayes, who countered Crozier's call, said, "Adam seemed to be in denial about the impact the changes are having on people's lives and doesn't seem to recognise that his workforce is deeply disgruntled."

The talks come days after Royal Mail said that around 30m letters, the equivalent of 40% of the average daily postal volume, have been delayed as a result of nationwide strike action.

The dramatic effect of the recent strikes comes as the Communication Workers Union (CWU) revealed that next week's three-day strikes would begin at 4am on Thursday (29 October).

The union has said that talks at ACAS could bring the postal dispute to an end.

Dave Ward, CWU deputy general secretary, said: "We have six days before any further strike action would take place. Given the progress we were making in talks earlier this week this should be enough time to reach an agreement.

"We want to go to ACAS with no preconditions on either side to resolve this dispute."

More than 43,000 UK staff across in mail centres, delivery units in mail centres, network logistic drivers and garage staff will strike on Thursday while 77,000 delivery and collection staff will walk out on the Saturday.

Mark Higson, managing director of Royal Mail, previously said: "My door is open and my phone is on and I am urging them again today to meet me so that we can all sign that agreement, get the strikes stopped and give us some peace in which we can get on with delivering Christmas for our customers.

"We have an agreement that was reached on Tuesday night and we had an agreement in 2007 - the real issue is not about getting agreements, it’s about the CWU leadership’s ability to deliver and honour them."

Earlier this week, Business secretary Lord Peter Mandelson warned that any prolonged strike action by Royal Mail members could force the Department for Health and NHS Trusts to look elsewhere for its delivery services.

"I very much regret what is happening. Candidly, I think it is totally self-defeating for our postal services and those who work to deliver them," he said.