PARTY loyalties will be tested today over the Britain's future in Europe as the countdown to this summer’s referendum hots up.

Brighton and Hove's three MPs have presented a unified front calling on city residents to vote remain to stay in the EU.

Green Caroline Lucas, Tory Simon Kirby and Labour's Peter Kyle said remaining would benefit the “internationally facing city” - despite the institution’s “shortcomings”.

But some of their party colleagues will be standing on the opposing side as the official launch of the Vote Leave campaign takes place in Brighton later today.

The leader of the House of Commons Chris Grayling will join dozens of local Conservative, Labour, Liberal Democrats and Green representatives, as well as students and business leaders at the launch in Pavilion Gardens from noon.

Former Conservative Brighton Kemptown MP Sir Andrew Bowden and senior Labour city councillor Tom Bewick are among who will be backing Brexit at the launch.

The city's three MPs said the disruption of Brexit could be “fatal” for many local small businesses, adding layers of bureaucracy, charges and custom rules when trading with the EU.

They also argue EU funding, including £650,000 funding for Wired Sussex, helped to support and nurture the city’s start-ups.

They said: “Ultimately it is our view that, despite some shortcomings, the EU is a positive force for small businesses.

“As MPs from three different parties we have many differences, but one thing we agree on is that our city is better off because of Britain’s membership of the European Union.”

Meanwhile Vote Leave supporters will today call on residents to “take back control" of the £350 million the UK sends to Brussels each week.

Cllr Tom Bewick said: “The truth is that, for most of the residents of Brighton and Hove, our membership of the EU has driven down wages, inflated house prices out of reach for far too many people, and resulted in unsustainable mass migration that places a huge burden on our local public services.”

Former Justice minister Mr Grayling added: “As home to a multitude of party political conferences over the decades, representative democracy is in the lifeblood of this city.

“I hope that residents will take note of this leading group of local leaders, who know from first-hand experience what a stultifying effect the EU has on the city’s ability to promote jobs and growth.”