By Darren Staples and Phil Noble
STOKE-ON-TRENT/WHITEHAVEN, England (Reuters) - Britain's opposition Labour Party and the populist UK Independence Party suffered damaging defeats at separate parliamentary by-elections on Friday, raising serious questions about the long-term electoral prospects of both parties.
Labour won the Stoke-on-Trent Central seat by a comfortable albeit reduced margin over the anti-European Union UKIP which had fielded its leader and had been hoping to capitalize on the area's staunchly pro-Brexit stance.
But, Labour lost a seat in the north western English region of Copeland where they have held power since 1935, giving Conservative Prime Minister Theresa May the first gain for a ruling party at a by-election in 35 years.
The victory for Labour in Stoke fueled doubts that UKIP, which has had a dramatic impact on British politics in the last decade playing a major role in bringing about last June's EU referendum and the vote to leave, can turn that influence into seats in parliament.
UKIP's former leader and best-known figure Nigel Farage had warned last week the Stoke vote was vital for the party's future.
The former industrial city in central England had been a safe Labour seat since 1950, but the party's support for staying in the EU put it at odds with 70 percent of Stoke voters who backed Brexit.
However, UKIP failed to capitalize on the anti-establishment sentiment it tapped so successfully when persuading voters to back Brexit last year, despite pouring resources into the campaign and putting party leader Paul Nuttall forward as its candidate.
"UKIP's time will come ... there's a lot more to come from us, we're not going anywhere, I'm not going anywhere," Nuttall told reporters after the result.
He said the seat was only ranked 72 on UKIP's list of target seats.
In Copeland, a rugged coastal region whose fortunes are hitched to the local nuclear power industry, May's Conservatives won in a region where they had been unsuccessful for 80 years.
Labour's grip on the area has weakened with the decades-long decline of the local mining, steel and fishing industries, but Thursday's vote proved a tipping point that will heap renewed pressure on left-wing Labour leader Jeremy Corbyn who only saw off a leadership challenge last September.
"To win power to rebuild and transform Britain, Labour will go further to reconnect with voters, and break with the failed political consensus," Corbyn said in a statement after the result.
Academic and polling expert John Curtice said Labour had lost votes yet again in polls held since the Brexit vote in which Corbyn had been criticized for his lukewarm support for the party's campaign to stay in the EU.
"We're left with an opposition that is losing votes in by-election after by-election ... all very different parts of England but the message to Labour is the same," Curtice told BBC TV.
"Meanwhile UKIP are now facing the possibility that the rewards of the fact that the majority of the country voted to leave may go to the Conservative Party."
(Writing by William James; editing by Michael Holden)