Around 25,000 people are eligible to cast ballots for candidates from two parties, as well as an independent, who are vying for representation in the 17-seat parliament in the enclave on Spain’s southern tip, dubbed “the Rock” because of its famous cliff-faced mountain.

Polls have consistently put the ruling centre-left Socialist-Liberal alliance neck-and-neck with the opposition centre-right Gibraltar Social Democrats.

Polling stations open at 9:00 am (0700 GMT) and will close at 10:00 pm, with the results expected early on Friday.

Fabian Picardo, the incumbent chief minister, who has headed the government of Gibraltar since 2011, has warned that the talks over Gibraltar’s post-Brexit future would suffer a setback if his alliance was ousted from power.

“Do you really think that what you want to do on Friday is wake up to a new negotiating team on the most complex negotiation that Gibraltar has been involved in its history?” he asked in one of his final campaign appearances.

Gibraltar, which has a land border with Spain, has been in limbo since Britain’s withdrawal from the EU in 2020 left it outside the bloc’s customs union and without guaranteed free movement of people.

Under a temporary agreement, Spain has granted free border passage to workers and tourists to avoid disruption, but this could be rescinded at any time.

The talks are aimed at agreeing a common travel area between Gibraltar and the so-called Schengen passport-free zone, which covers most of the EU’s member states along with four other European nations.

With the protocol on Northern Ireland agreed by London and Brussels earlier this year, Gibraltar now stands in isolation as the last British territory left without a deal that clarifies its future relationship with the EU and with its neighbour Spain.

Keith Azopardi, leader of the opposition Gibraltar Social Democrats and a former deputy chief minister of Gibraltar, has blasted Picardo for failing to reach an agreement, vowing his party would deliver a “safe and beneficial” deal.

The British territory relies on around 15,000 workers — most of them European, making up half of Gibraltar’s workforce — who cross the border with EU-member Spain every day.

Fluidity at the border is also key for tourism.    

Gibraltar, which is strategically located at the western gateway to the Mediterranean Sea, welcomes millions of visitors every year.

Spain ceded Gibraltar to Britain in 1713 under the Treaty of Utrecht but has long argued that it should be returned to Spanish sovereignty.