Labour has opened selections for three more sought-after marginal seats that it is aiming to take from the Tories as part of Jeremy Corbyn’s push for Downing Street.

All three seats across more affluent parts of the north – Bolton West; Shrewsbury and Atcham; and Southport – have been named as all-women shortlists.

Corbyn has vowed to select candidates for 75 marginals by Christmas as speculation continues that Theresa May’s government could collapse after any Brexit deal.

The guessing-game around the future of May’s minority government has intensified this week following the resignation of Sir Michael Fallon as defence secretary over his behaviour towards women as well as allegations over impropriety made about Damian Green, May’s de facto deputy, who denies any wrongdoing.

The smallest majority of the three seats at the last election was in Bolton West, where Corbyn visited this summer, above. Julie Hilling was MP until 2015 and failed by just 936 votes to recapture the constituency in June.

The three new Labour selections all have a deadline of later this month to apply:

Bolton West: November 17.

Shrewsbury and Atcham: November 20

Southport: November 13

The full list of Labour target seats where selections have begun