The Labour ex-cabinet minister said Gibraltar was unlikely to be a key facet of Brexit negotiations over the next two years.
He intervened following ex-Tory leader Michael Howard’s outlandish claim that Theresa May would go to war to protect the territory’s sovereignty, amid increased tension around its status in the wake of the decision to trigger Article 50.
Speaking to BBC Radio 4's Today programme Mr Straw said: “The idea of Britain going to war, or Spain going to war against Britain, over Gibraltar is frankly absurd and reeks of 19th century jingoism.”
He added: “I doubt very much that Gibraltar will be the deal breaker."
Mr Straw went on to point out that Spain had a large trade surplus with the UK in goods and services and would likely be unwilling to disturb it for the sake of a statement on Gibraltar.
He later said: “This is 2017/18 not 1851, when Palmerston sent gunboats to shell the Piraeus, because the Greeks wouldn’t comply with a request for compensation for one British individual, born in Gibraltar by the way, who had been refused that compensation when his house was sacked by rioters.
“Those days are long gone.”
The Prime Minister was forced at the weekend to reiterate the UK’s “steadfast commitment” to Gibraltar after Mr Howard caused embarrassment by suggesting the UK could go to war with Spain over the territory as it had done with Argentina over the Falklands.
Mr Howard told Sky News: “Thirty-five years ago this week, another woman prime minister sent a taskforce halfway across the world to defend the freedom of another small group of British people against another Spanish-speaking country, and I’m absolutely certain that our current Prime Minister will show the same resolve in standing by the people of Gibraltar.”
And Foreign Secretary Boris Johnson said on Monday: "I think the position of the Government is very, very clear. Which is that the sovereignty of Gibraltar is unchanged and it's not going to change, and cannot conceivably change without the express support and consent of the people of Gibraltar and the United Kingdom."
Gibraltar’s First Minister Fabian Picardo had said the possibility of shared sovereignty with Spain would “strip of us who we are” before adding that “the United Kingdom goes to war over the principle of consent all around the world”.
A Downing Street spokesperson said Theresa May had spoken to Mr Picardo that morning, and said she would “never” allow Gibraltar to share sovereignty with Spain, for as long as Gibraltar’s people did not wish for that to be the case.
On Friday morning, European Council President Donald Tusk published his draft guidelines for the forthcoming negotiations with the EU, which said Spain would be given a veto over any deal that would affect the status of Gibraltar.
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