The government could face the threat of postal strikes later this year, as union leaders consider tabling a "substantial" pay claim to the Royal Mail.

The Communication Workers Union warned on Monday that such a claim would be tabled in October, and would seek to increase the basic salary of postal workers from its current level of £261 per week to £300 per week.

"The mood is that come October we will be looking for a substantial increase and we will be prepared to back that up with industrial action," said David Ward, the newly-elected deputy general secretary.

"We don't believe that our employers think we are serious on pay but the membership is undoubtedly very restless."

There are a number of pay-related issues still outstanding between Royal Mail and the union.

Workers have still not agreed to the prospect of earning an extra £20 per week for accepting new delivery rounds, while the CWU has not accepted a new system in which the second post will be scrapped, expressing concern about the resultant increase in length of the first post rounds and the health of staff as a result.

The threat of industrial action over pay comes after the company announced in May that it had halved its losses over the last financial year.

The postal service now loses an average £750,000 per day, compared to £1.2million the year before.

"We're largely still being pretty inefficient but this is the first time in five years the numbers have gone in the right direction," chairman Allan Leighton told the BBC as the announcement was made.

"I'm pretty confident we'll be profitable this year."

However, at the same time the company warned that there was still a £4.6billion black hole in its pension fund.

"We've been saying for ages that we'd like to get the basic salary up for all our postmen and women to £300 per week but it is a question of doing it when the company has the funds to do it," a Royal Mail spokeswoman told ePolitix.

"We will wait to see what the pay claim is when it comes in."