Source tells IBTimes UK that deputy Labour leader told Corbyn of a possible leadership challenge.
Thornberry was promoted from shadow secretary for defence in the Labour reshuffle by Jeremy Corbyn.
Left-wing leader has vowed to stay on as he faces a coup attempt after the EU referendum result.
Top Conservative says there is no need to trigger Article 50 until a new prime minister is elected.
Pound falls against dollar and more Labour resignations expected in latest Brexit reactions.
Labour pressure group Momentum have signed up more than 3,000 people to the demonstration.
Kuala Lumpur says Malaysian authorities are looking into the aerial encounter with Indonesian jets.
French and German leaders are on the same page over handling the situation arising out of Britain's EU exit.
Clinton slammed Trump's Brexit response, saying he is looking out for his businesses and not the American people.
Mariano Rajoy's Partido Popular claims victory but overall majority failure adds further uncertainty in Europe.
In his weekly Telegraph column, Johnson said EU citizens would be protected in the UK, and vice versa.
A young girl in the vehicle survived the crash and was airlifted to the hospital in critical condition.
UK government should be given time to weigh up the consequences of a Brexit, says German official.
The Texas Nationalist Movement hopes to copy the Leave campaign's effort to secure vote in 2018 election cycle.
Chris Bryant is the 12th member of shadow cabinet to leave job in protest at Corbyn's party leadership.
Labour deputy Tom Watson says he will meet Jeremy Corbyn on Monday 27 June to discuss 'way forward'.
Conservative grandee says only pro-Brexit leaders have 'credibility' to negotiate with Europe
Other candidates include David Miliband and Angela Eagle, while John McDonnell has ruled himself out.
Former work and pensions secretary denies major Leave campaign's promise
Pro-Biafrans call for independence of territories forcibly annexed to Nigeria during British colonisation.
German politician Martin Schulz wants the two-year process of leaving to get started as soon as possible
Farron promises to hold a new Brexit vote if it gets into power in a general election.
The resignations follow Hilary Benn's sacking as shadow foreign minister
Labour leader facing open revolt as Hilary Benn, Heidi Alexander and others leave shadow cabinet.
SNP leader believes Scotland Act 1998 might give Holyrood power to stop the UK leaving the EU.
New Delhi lawmakers belonging to Aam Aadmi Party (AAP) protest against alleged political witch-hunt.
The volume of signatures caused the UK petition website to crash.
As some Labour MPs publicly revolt against their leader, the membership bites back.
McDonnell also ruled out running as Labour leader if Corbyn was forced out
The shadow foreign secretary was sacked by Corbyn early on Sunday morning.