The UK Labour party’s leadership crisis burst into the open on Wednesday as David Miliband repeatedly refused to rule out a challenge to Gordon Brown, setting the for­eign secretary at direct odds with the prime minister.

Mr Miliband’s failure to offer Mr Brown unequivocal backing was widely seen at Westminster as the start of a leadership bid, following the party’s disastrous by-election defeat by the Scottish Nationalist party in Glasgow East last week.