Mounting pressure on UK Prime Minister Sir Keir Starmer threatens to rattle financial markets, hit the pound, and reignite investor fears over Britain’s political and fiscal stability, warns the CEO of deVere Group, one of the world’s largest independent financial advisory and asset management organisations.
The warning from Nigel Green comes after Labour MP Catherine West dramatically declared she would attempt to trigger a leadership contest against Starmer if no cabinet minister steps forward by Monday to challenge him, following devastating local election results for the governing party.
Her intervention has detonated speculation inside Westminster over Starmer’s grip on power and raised the prospect of a destabilising internal struggle at the heart of government just months after Labour returned to office.
Nigel Green says markets are unlikely to dismiss the developments as mere political noise if the rebellion gathers momentum.
“Financial markets can tolerate unpopular governments. They can tolerate weak poll numbers. What they struggle with is uncertainty over leadership, economic direction and fiscal discipline.
“Sterling and UK government bonds, or gilts, become vulnerable the moment investors sense control is slipping.”
West has reportedly secured the backing of around 10 Labour MPs prepared to support a leadership challenge, still far short of the 81 required to formally trigger a contest.
However, investors are acutely aware political crises can escalate rapidly once public dissent emerges inside governing parties.
The concern for markets is not Catherine West herself, but what her intervention potentially signals: fractures opening inside a government that has worked hard to present itself as stable, disciplined and economically credible.
Under Starmer and Chancellor Rachel Reeves, Labour has carefully cultivated market confidence by projecting fiscal restraint, avoiding radical spending promises, and maintaining a comparatively business-friendly stance.
Any threat to that framework risks provoking immediate market reactions.
“The current leadership has spent considerable political capital convincing investors Britain has moved away from the instability and fiscal recklessness associated with previous crises,” explains the deVere chief executive.
“If investors begin to fear a leadership vacuum, ideological infighting or a shift toward looser spending policies, markets could react fast and aggressively.”
Currency traders would likely move first.
“Sterling is highly sensitive to political credibility because the UK runs persistent deficits and depends heavily on international capital flows. Political instability can rapidly undermine confidence in British assets.”
Analysts say the pound could come under pressure against the dollar, Swiss franc and Japanese yen if leadership uncertainty intensifies during the coming days.
UK government bonds are also exposed.
Previous bouts of speculation surrounding Starmer and Reeves triggered weakness in gilts as investors worried about the possibility of alternative leadership teams pursuing more interventionist or less disciplined economic policies.
Markets remain deeply scarred by the fallout from the September 2022 Liz Truss mini-budget crisis, when a collapse in investor confidence sent borrowing costs soaring and forced emergency intervention from the Bank of England.
“Britain remains unusually vulnerable to political credibility shocks because investors remember exactly how quickly confidence evaporated during the Truss budget crisis,” says Nigel Green.
“Bond traders are now almost conditioned to react swiftly to any sign fiscal discipline could weaken.”
Attention is already turning toward possible successors.
Health Secretary Wes Streeting, Deputy Prime Minister Angela Rayner and Greater Manchester Mayor Andy Burnham are all being discussed as potential contenders should pressure on Starmer intensify further.
Some investors may view candidates perceived as more left-leaning with caution, “particularly if markets begin to anticipate higher borrowing, heavier taxation or increased state intervention in the economy.”
At the same time, a failed rebellion that collapses quickly could ultimately strengthen Starmer by demonstrating he still commands overwhelming support inside Labour.
Cabinet Office Minister Nick Thomas-Symonds has already publicly warned colleagues against destabilising the government through leadership speculation.
For now, investors are watching Westminster with growing unease.
“The political risk premium attached to UK assets has fallen significantly since Labour entered government,” notes Nigel Green.
But, he concludes, political stability is fragile.
“Once doubts emerge over leadership and economic continuity, markets do not wait politely for Westminster to resolve itself.”
