A series of hugely influential Facebook advertising campaigns that appear to be separate grassroots movements for a no-deal Brexit are secretly overseen by employees of Sir Lynton Crosby’s lobbying company and a former adviser to Boris Johnson, documents seen by the Guardian reveal.

The mysterious groups, which have names such as Mainstream Network and Britain’s Future, appear to be run independently by members of the public and give no hint that they are connected. But in reality they share an administrator who works for Crosby’s CTF Partners and have spent as much as £1m promoting sophisticated targeted adverts aimed at heaping pressure on individual MPs to vote for a hard Brexit.

Repeated questions have been raised about who is backing at least a dozen high-spending groups that have flooded MPs’ inboxes with calls to reject Theresa May’s deal. Until now they were thought to be independent entities.

But according to the documents, almost all the major pro-Brexit Facebook “grassroots” advertising campaigns in the UK share the same page admins or advertisers. These individuals include employees of CTF Partners and the political director of Boris Johnson’s campaigns to be mayor of London, who has worked closely with Crosby in the past.

Their collective Facebook expenditure swamps the amount spent in the last six months by all the UK’s major political parties and the UK government combined. They have paid for thousands of different targeted Facebook ads encouraging members of the public to write to their local MPs and call for the toughest possible exit from the EU, creating the impression of organic public opposition to Theresa May’s deal.

A pro-Brexit Facebook advert run by Britain’s Future targeted at Conservative MP Kwasi Kwarteng. Photograph: Britain's Future / Facebook

Crosby’s secretive lobbying company, CTF Partners, has come under increasing scrutiny in recent months. Leaked documents have revealed how it boasts of its ability to run fake online grassroots campaigns that encourage users to join an online community and then be “mobilised to communicate directly with key decision-makers”, whether to delegitimise the Qatari government or convince people that burning coal is good.

Political strategist Sir Lynton Crosby, the co-founder of CTF Partners. Photograph: Oli Scarff/AFP/Getty Images

The Australian political strategist helped run the last four Conservative general election campaigns, helping to secure an unexpected majority government for the party in 2015.

He has recently been repeatedly linked to a potential Conservative leadership campaign by Johnson, having been lined up to run the former foreign secretary’s abortive 2016 bid for the same position. CTF Partners gave Johnson an interest-free loan of £23,000 – subsequently repaid – in January, while the company already employs arch-Brexiter former Tory MP Stewart Jackson in an advisory role and paid for the former Brexit secretary David Davis to go on trips.

Mainstream Network attracted attention last year when it was exposed for spending at least £250,000 to reach more than 10 million voters with adverts urging voters to email their local MP and urging them to “chuck Chequers”, alongside articles criticising George Soros’s involvement in the remain campaign. After it attracted attention it was abruptly shut down.

A Facebook ad placed by Mainstream Network in 2018 urging members of the public to contact their MP and reject Theresa May’s Chequers deal. Photograph: Mainstream Network/89up/DCMS select committee

Although Facebook has substantially increased the level of transparency around political advertising in recent months, all that is required to run such a campaign is a publicly named individual who is registered to a UK postal address or contact details for a public organisation. There is no true disclosure around a campaign’s financial backers and no UK law requiring financial transparency outside an election period.

After the closure of the Mainstream Network site, similar adverts began appearing on a Facebook page named Britain’s Future, whose public frontman is a former Two Pints Of Lager and a Packet of Crisps scriptwriter named Tim Dawson who later became a Conservative council candidate.

The group hit the headlines last month when it was revealed it was the biggest single UK political advertiser on Facebook, spending £422,000 on adverts campaigning for a hard Brexit despite never declaring its financial backers.

According to documents seen by the Guardian, individuals with the ability to place adverts on both the Mainstream Network and Britain’s Future page include Reuben Solomon, whom multiple sources identified as an employee of Crosby’s CTF Partners.

He did not respond to a request for comment but a relative, who previously lived with him at an address in north London, confirmed to the Guardian that Solomon worked for Crosby.

Facebook adverts placed by Britain’s Future and targeted at voters in Labour constituencies, urging them to contact their MPs and demand a hard Brexit. Photograph: Facebook / Britain's Future

According to the documents, other individuals with oversight of the Mainstream Network Facebook page include Charles Carroll and Alex Crowley.

Carroll, who deleted his LinkedIn profile after the Guardian began to seek comment for this article, also works for Crosby’s CTF Partners, according to a cached version of the page.

Crowley was employed by Boris Johnson as his political adviser during his period as mayor of London, later writing a book about his experience working closely with Crosby on campaigns. He later went on to run a political campaigning company and became political director on Zac Goldsmith’s ill-fated mayoral bid.

The Brexit supporter said his involvement in Mainstream Network was because “some who disliked the result have been actively trying to overturn it”. He did not comment on his links to Crosby but said: “I wanted to see the result actually delivered and give a voice to that majority so the democratic result is honoured.”

Dawson, the public face of Britain’s Future, declined to comment on who has funded his enormous Facebook ad campaign or whether it was linked to Crosby or the Mainstream Network, instead saying he simply wanted to represent 17.4 million Brexit voters, adding: “This is my way of getting the point across to those in Westminster that the government should honour its manifesto and that the current deal is not what we voted for.”

Solomon, the CTF employee, is also connected to a page called We are the 52%, which has spent more than £50,000 on pro-Brexit Facebook adverts and is fronted by a Conservative activist and former Vote Leave staffer Theodora Dickinson.

Dickinson declined to comment on any links between her group and Crosby’s company but said remain campaigners “are using similar tactics and spending more” without fully declaring their financial backers, highlighting the £370,000 expenditure on Facebook adverts by the People’s Vote campaign and the £300,000 spent by Best for Britain.

A Facebook ad demanding a hard no-deal Brexit posted by the We are the 52% campaign group. Photograph: We are the 52% / Facebook

Solomon is also listed as an administrator on at least a dozen other pro-Brexit pages, which typically mix campaigning content with other unrelated interests and appear to have also spent money running an unknown number of pro-Brexit adverts. Pages used for the messaging include Small Business for Great Britain, Northern Industry, and Protecting British Heritage.

The House of Commons digital, culture, media and sport select committee, which has led the way on investigating online disinformation, has repeatedly called for Facebook to reveal the identities of those who were funding Mainstream Network, suggesting they crossed an ethical line.

“I believe there is a strong public interest in understanding who is behind the Mainstream Network, and that this information should be published,” the committee’s chairman, Damian Collins, said last month after Facebook refused to identify the individuals behind the page.

“People should have a right to know who is targeting them with political advertisements and why. That is why the committee had called for a change in the law to outlaw these kind of dark adverts from secret campaigns,” he said.

Although the documents point towards the individuals who are running the campaigns, it remains unclear who is ultimately picking up the substantial bill for this attempt to persuade MPs there is a grassroots uprising for a hard Brexit.

CTF Partners, Carroll, and Solomon did not respond to requests for comment.