In an interview with AFP in London, Gibraltar's Chief Minister Fabian Picardo dismissed Spain's offer of joint sovereignty as a way of keeping the pro-EU peninsula within the European Union.
But he did not rule out having an associate status with the EU once Britain leaves the bloc, in order to keep things moving at the border -- something critical for Gibraltar's economy.
Though Spanish politicians described joint sovereignty as a generous offer, "this is the generosity of a predator that thinks that its prey is now ready to surrender", Picardo said.
"It's not generous to tell someone to surrender the thing that is most valuable to them at the time you think they may be in need of your assistance."
Picardo was in London this week to face questions from the British parliamentary committee scrutinising the Brexit process.
The 44-year-old also attended the presentation of a report about the impact Brexit will have on the "Rock", as the territory is nicknamed after its 426 metre (1,398-feet) high limestone ridge.
Daily Spanish influx
The seven square-kilometre peninsula on the tip of Spain's south coast, home to 33,000 people, was ceded by Spain to Britain in 1713 in perpetuity.
Spain, which maintains its sovereignty claim, shut its border gates with Gibraltar in 1969.
It fully reopened them in 1985 ahead of Spain joining the European Economic Community, the EU's predecessor, the following year.
Gibraltar's thriving services-based economy, which hosts several big insurance and online betting firms, relies in large part on access to the EU's single market.
It also depends heavily upon the 10,000-strong mostly Spanish workforce coming through the sole crossing on the 1.2-kilometre border.
Many come from the neighbouring Campo de Gibraltar area of Andalusia, where unemployment is high.
Gibraltar accounts for 25 percent of the Campo's gross domestic product and is the "second biggest employer in Andalusia after the regional government", Picardo said.
For this reason, he believes Spain would not want to see Gibraltar damaged by Brexit, and would also not want to re-close the border.
"I don't think that there is anyone as stupid in Spain as to try that tactic again," he said.
When the late dictator Francisco Franco shut the gates, "Gibraltar got stronger and more British in the process".
Still, in the June referendum, 96 percent of voters in Gibraltar wanted Britain to remain in the EU.
From Gibraltar's current relationship with the EU, Picardo now wants to retain access to the British market and UK services, freedom of movement across the EU, "frontier fluidity" with Spain, and access to the European single market, if Britain has it.
But British Prime Minister Theresa May says she wants to pull out of the single market and most of the customs union arrangements in order to control immigration, then negotiate a new free trade agreement with the EU.
"One of the possibilities as we explore the future is that we might have an associate-style status with the EU, simply because that is how the EU treats other microstates like the Vatican City, Liechtenstein, Andorra, Monaco," said Picardo.
Those tiny nations have "different degrees of participation with the EU", he explained.
He noted that they are not technically within the Schengen open borders area, but are treated as if they were. Some are also in the customs union and others not.
In any case, despite the Brexit referendum outcome, staying British remains the red line for the fiercely loyal Gibraltarians.
"Exclusive British sovereignty over Gibraltar is a sine qua non," Picardo said.