UNDER-FIRE Jeremy Corbyn says he accepts some of the blame for Labour's Copeland by-election defeat – but insists he won't quit as leader.

He has come under mounting pressure after the Cumbrian seat – a Labour stronghold for more than 80 years – was seized by Conservative Trudy Harrison in Thursday's by-election.

Mr Corbyn said he took his "share" of blame for that defeat and conceded that Labour had not yet done enough to rebuild trust with voters.

Writing in the Sunday Mirror , he said: "Labour's share of the vote in Copeland has been falling for 20 years and, of course, I take my share of responsibility.

"Both these areas (Copeland and Stoke), like many others, have been left behind by globalisation and lost out from a rigged economy.

"We haven't done enough yet to rebuild trust with people who have been ripped off and sold out for decades and don't feel Labour represents them."

As the Copeland defeat was analysed over the weekend, former Labour foreign secretary David Miliband said blow proved the party was further from power than any time in the past 50 years.

He was "deeply concerned" after Mr Corbyn made it clear he is determined to continue as leader despite the loss.

But, in rallying cry to his party, Mr Corbyn insisted that "now is not the time to retreat, to run away or give up".

Speaking at the Scottish Labour Party conference in Perth, he stated: "Comrades, let us never forget it's not called the struggle for nothing."

In an interview with Sky later, Mr Corbyn said he would definitely be Labour leader for the 2020 general election.

Mr Corbyn spoke after his deputy Tom Watson publicly challenged Unite union boss Len McCluskey and others to back the under pressure leader.

Mrs Harrison, meanwhile, is expected in Westminster for her first day at work in Parliament today. She has been urged to make protecting health services a priority.