Zac Goldsmith’s claim to be an “independent” by-election candidate has been dealt a blow after it emerged Conservative MPs have been campaigning alongside him.

Mr Goldsmith triggered a by-election in Richmond Park after the Government confirmed it would expand Heathrow airport, which is unpopular locally due to the noise pollution it causes.

On paper he has stood as an “independent” candidate opposed to Government policy, but his rivals in the seat claim that once returned to Parliament he would still have strong links to the Conservatives.

The suspicions were given credence this week after a photograph posted on social media and reported on the politics.co.uk website showed Mr Goldsmith campaigning alongside a brace of serving Tories.

Theresa Villiers, the former Northern Ireland secretary and Tania Matthias, another West London Tory MP, were among MPs pounding pavements with the nominally independent candidate.

Jacob Rees-Mogg, a high-profile Tory backbencher, was also present campaigning for Mr Goldsmith.

Mr Rees-Mogg’s appearance will raise particular eyebrows because he has a strong history of backing the expansion of Heathrow.

In September the Tory described a third runway at the airport as “essential for the nation” and celebrated the suggestion that “the prospect of Brexit will speed the third runway upon its way”.

Furthermore the Conservatives are not opposing Mr Goldsmith’s candidacy in the seat. Mr Goldsmith also has the backing of his local Conservative association in Richmond Park.

The Liberal Democrats, who are Mr Goldsmith's main opponents in the seat having held it until 2010, said the Tory support for Mr Goldsmith undermined his claim to be independent.

“This picture shows clearly the Brexiteers uniting," a party spokesperson told The Independent.

“The Hard Brexiteers are worried that the election is slipping away from Goldsmith and they have been drafted in to help him.

“He's an independent in name only and is being backed by Tory HQ and UKIP.”

A Liberal Democrat source also pointed out that nine out of the 10 names on Mr Goldsmith's election nomination form were senior Conservative councillors, former candidates or activists.

But Mr Goldsmith, who was accused of running a "racist" campaign for Mayor of London earlier this year, hit back at the claims through a spokesperson.

In pictures: 70 years of Heathrow Show all 22 1 /22 In pictures: 70 years of Heathrow In pictures: 70 years of Heathrow Inside one of the terminal tents in 1946 The year the airport opened. Comfortable armchairs and flowers try to distract from the conditions Graham Bridges collection In pictures: 70 years of Heathrow An aerial view of the airport in 1949 Construction of the runway layout and Central Area are under way In pictures: 70 years of Heathrow A Pan Am crew checks out the Boeing Stratocruiser N1029V Clipper Golden Eagle in 1954 During the early 1950s, Pan Am and American Overseas Airlines operated Statocruisers into London Airport in direct competition on the North Atlantic route operated by BOAC In pictures: 70 years of Heathrow One of the first official London Airport guidebooks C.1953, priced 1s In pictures: 70 years of Heathrow In 1950 a permanent concrete terminal building was built This replaced the tents previously used at London Airport North and is seen still in use for charter and cargo flights in this 1959 view via Graham Bridges In pictures: 70 years of Heathrow BOAC check-in desk in 1954 Inside the new London Airport North terminal building, just before the move to the Central Area Graham Bridges collection In pictures: 70 years of Heathrow Air traffic control tower in the 1960s Inside the visual control room CAA Archives via Pete Bish In pictures: 70 years of Heathrow Rear cover of the 1956 guidebook Showing a plan of the airport at the time, with entrance prices to the spectators’ viewing terraces and for airport coach tours In pictures: 70 years of Heathrow Spectators in 1958 How close can you get? As soon as the Central Area was open, spectators were afforded unprecedented views of the airliners In pictures: 70 years of Heathrow Terminal 3 was opened as the Oceanic Terminal on 13 November 1961 It was built to handle flight departures for long-haul routes. Renamed Terminal 3 in 1968, it was expanded in 1970 with the addition of an arrivals building In pictures: 70 years of Heathrow Inside Terminal 3 in 1969 Check-in desks for BOAC and QANTAS airlines In pictures: 70 years of Heathrow Plane spotting on Heathrow’s viewing terraces in the 1960s Wrap up warm, take your spotting logbooks, pen and binoculars and get your mum to pack your sandwiches In pictures: 70 years of Heathrow No 1 Passenger Building Also called the Europa Building. In this photo, taken on 22 June 1963, flags of the many airlines it serves are flown Lee Holden In pictures: 70 years of Heathrow Luggage-trailer-towing Routemaster buses When BEA and BOAC merged to form BA on 1 April 1974, both fleets had to be repainted in the new livery, but so did all the ground support equipment In pictures: 70 years of Heathrow The entrance to the traffic tunnel in 1974 A Lufthansa Boeing 737 is seen on the runway In pictures: 70 years of Heathrow A 40 per cent scale model of Concorde In September 1990 it was erected on the roundabout at the entrance to the tunnel that passes under the northern runway at Heathrow Airport. It was built in four main parts, with an 80ft-long central fuselage section, to which the wings and tail fin were attached. The completed model was placed on the roundabout in September 1990 and was monitored by CCTV and surrounded by an infrared perimeter alarm that was connected to the local Heathrow police station to ensure it was not vandalised In pictures: 70 years of Heathrow Heathrow Airport's 50th anniversary On 2 June 1996, Heathrow marked its anniversary with a flypast of representative airliner types that have served the airport over the years. This culminated in a formation flypast by Concorde with Hawks of the RAF Red Arrows aerobatic team In pictures: 70 years of Heathrow The roof of Terminal 3’s car park One of the last bastions for plane spotters and spectators was here. This is the unfriendly notice that greets anyone who attempts this today Richard Vandervord In pictures: 70 years of Heathrow On 24 October 2003 BA withdrew its Concordes from service The final scheduled commercial flight was BA002 from JFK operated by G-BOAG. Here we see three of the Concordes parked together outside the BA hangar on 8 November 2003 following withdrawal John Hughes In pictures: 70 years of Heathrow The new control tower Costing £50 million to construct, it gives controllers an excellent 360-degree panoramic view NATS photograph In pictures: 70 years of Heathrow The new Terminal 2 The Queen’s Terminal In pictures: 70 years of Heathrow Looking due west down Runway 27L

"Zac's standing as an independent candidate on a matter of principle has attracted cross-Party support and help," the spokesperson said.

"The Conservative Party has said publicly that backbenchers could make their own decision on whether to support Zac.

"Many are doing so because they respect the fact that he is keeping a pledge to voters to lead the fight against any expansion at Heathrow.

"There is no secret about the picture on which this story is based: it was posted on social media by Zac's team. More than half those in the picture are actually remainers,"