Under-performing civil servants could be incentivised to leave their jobs under new government plans, while top staff will have their pay linked to their performance.

Cabinet Office minister Pat McFadden said they will "fundamentally reshape" the service as its state is currently not "match-fit" for what the country needs.

The plans are part of wider reforms expected to be set out next week and will go alongside what officials call the prime minister's "intervention" on Thursday.

A union has accused the government of delivering a "soundbite, not a credible plan for change", describing the plans as "retreading of failed narratives".

In a system designed to give employers the tools to deal with bad performance, McFadden, who will appear on Laura Kuenssberg's Sunday show, is expected to promise a new "mutually agreed exits" process, that will see civil servants performing below their requirements, incentivised to leave their jobs.

Meanwhile, under-performing senior civil servants will be put on development plans, with the possibility of being sacked if there is no improvement within six months.

The Chancellor of the Duchy of Lancaster is also expected to say that the most senior officials will have their pay linked to performance outcomes.

"The state is not match-fit to rise to the moment our country faces," McFadden explained, adding that the government's "plan for the civil service is one where every official is high performing and focused on delivery".

"To do this we must ensure that we go further to ensure those brilliant people who can deliver are incentivised and rewarded, and those who can't are able to move on.

"The changes announced today will result in a more focused and productive civil service and more efficient delivery of the change working people need."

McFadden is also expected to pledge to make more public services digitised and employ more staff in relevant roles.

But Dave Penman, general secretary of the civil servants union FDA, said: "If the government is serious about transforming public services they must set out what the substance of reform looks like, not just the retreading of failed ideas and narratives."

He added that meaningful reform "must put substance before headlines", and that if McFadden wanted civil servants to focus on delivery - while government departments simultaneously cut resources - "ministers need to set realistic priorities".

"[The] government should get on with the difficult job of setting those priorities rather than announcing a new performance management process for civil servants every other month," Mr Penman explained.