As the CWU prepare to take legal action against Royal Mail's use of 30,000 relief staff the Telegraph reports that more than a quarter of postal workers are expected to break the strike later this week.

It comes as Royal Mail launch an advertising campaign to encourage its staff to go to work.

The Royal Mail spent tens of thousands of pounds placing full-page adverts in all national newspapers appealing to its staff to defy the postal union by crossing the picket line later this week.

The Communication Workers Union has called out its 120,000 members on two more days of national strikes, on Friday this week and Monday next week.

This will take the industrial action into its fourth week, risking crippling the Christmas post for many consumers and severely damaging many small businesses that rely on the post.