The Mayor of London has repeated his offer to put a team in charge of the "failing" Southern Railway.

Sadiq Khan wrote to Transport Secretary Chris Grayling, reiterating the urgency of putting Transport for London (TfL) temporarily in control of the franchise, run by Govia Thameslink Railway, after months of disruption caused by industrial action and a shortage of staff.

He said that, in any other walk of life, the service offered to paying customers by Southern would not be tolerated.

The Mayor believes TfL is best placed to sort out the problems, saying it would "get a grip" on the situation as it has expertise in running public transport services relied upon by millions of people.

A previous offer was rejected by the Government.

Mr Khan's letter criticised the Government's refusal to look into changing the management of the franchise, saying TfL can deliver a better service than Southern Rail by "immediately assigning an experienced team to fix the service".

It urged the Department for Transport to take action immediately as "passengers should not have to suffer any longer the appalling level of service they are currently forced to endure".

Members of the Rail, Maritime and Transport union staged three days of strikes this week in a dispute over the role of conductors.

Talks aimed at resolving the row are being held at the conciliation service Acas.

A spokesman for the Rail Delivery Group, which represents train operators and Network Rail, said: "The challenges facing the Southern network - modernising services and operating trains during major improvement work to transform London Bridge - would remain the same whoever gets the franchise.

"We are keen to work with both the Department for Transport and Transport for London to make best use of the overall network to deliver joined-up services for our customers."