A network of secretive pro-Brexit Facebook campaigns overseen by Sir Lynton Crosby’s company CTF Partners was part of a wider campaign to undermine Theresa May and push Britain towards a hard Brexit, according to individuals with knowledge of the company’s operations and internal documents.

On Tuesday the information commissioner will answer questions in parliament about the network of Facebook campaigns through which seemingly independent pro-Brexit groups spent as much as £1m running online adverts promoting a hard Brexit on sites with names such as Britain’s Future and Mainstream Network.

The pages were designed to create the impression of a grassroots uprising for a hard exit from the EU and were fronted by supposedly independent pro-Brexit campaigners. However, they were overseen by staff at Crosby’s company who were trying to influence MPs in votes on Brexit.

Crosby, an Australian political strategist and longtime confidant of Boris Johnson who played a role in convincing the former foreign secretary to back Brexit, received a knighthood for his work for the Conservatives in the 2015 general election. However, his reputation took a battering after returning for Theresa May’s disastrous 2017 election, prompting speculation he is positioning his company to benefit from placing Johnson in Downing Street – with the possibility that CTF could contribute resources if Johnson’s leadership campaign goes to a final vote.

The online pro-Brexit campaign will be the subject of the first hearing of the new dedicated House of Commons sub-committee on online disinformation, which has pledged to “scrutinise and examine threats to democracy” posed by online disinformation.

The Conservative MP Damian Collins, who chairs the committee, said: “We’ll be asking the ICO [information commissioner’s office] in particular for an update on its investigations into organisations like Mainstream Network and other Brexit campaigns from shadow organisations. We are also keen to know more about the information the ICO has received from Facebook relating to these campaigns.”

According to documents seen by the Guardian, some of the Facebook pages involved in the pro-Brexit network overseen by Crosby’s company have been running since late 2017, suggesting the online influence campaign to nudge Britons towards backing a hard Brexit may have been running for substantially longer – and as part of a much wider campaign – than previously thought.

Many of the pro-Brexit Facebook ads linked to Crosby’s company were deleted after the Guardian first reported on the existence of the groups, making it harder for MPs to hold CTF Partners to account for their historical campaigning activities. It has also drawn parallels with how key information relating to the conduct of online campaigns for the Brexit referendum was removed from the internet before it could be scrutinised.

Some staff at CTF are despairing of the revelation of Crosby’s involvement in the campaigns, and argue the lack of transparency around the activities is problematic. “The secrecy makes it a story,” one person said.

CTF Partners’ digital campaigns often involved running innocuous-sounding Facebook pages about Britain such as Small Business For Britain, Protecting British Heritage and Northern Industry and then using them to promote pro-Brexit messages to unwitting readers.

The campaigns appear to fit Facebook’s definition of “coordinated inauthentic behaviour”, a term used by the social network to justify the mass removal of influence campaigns linked to the Russian and Iranian governments. Despite this, Facebook has repeatedly declined to comment on whether it will be pursuing a similar course of action against pages run by Crosby’s company and banning them from the social network.

In addition to the pro-Brexit digital campaign, employees of CTF Partners have been advising key political figures in the European Research Group on how to choose the best messages and destabilise the prime minister. David Canzini, a Crosby employee, helped out with last summer’s “chuck Chequers” deal and was reported to have been involved in last December’s botched leadership challenge against May.

However, it remains unclear who ultimately picked up the bill for the expensive and time-consuming campaign, both online and in real life. Similar campaigns run by Crosby’s company have budgets running into millions of pounds.

There are also questions over how Crosby’s firm uses arm’s-length companies to run its digital campaigns. Since 2016 it has outsourced work to two rightwing New Zealand political activists called Ben Guerin and Sean Topham through their Auckland-based consultancy Topham Guerin, which bills CTF Partners for the work they do on behalf of Crosby’s company.

Guerin and Topham, both in their mid-20s, are regularly based in CTF’s Mayfair office. They also ran the digital campaign for New Zealand’s National party in the country’s 2017 general election, ultimately failing to stop the Labour leader, Jacinda Ardern, becoming prime minister.

Documents seen by the Guardian suggest Topham Guerin was also involved in running online pro-coal campaigns on behalf of mining giant Glencore to encourage the construction of coal-fired power stations, in addition to working in India and Malaysia.

Topham was previously the chair of the National party’s youth wing, while Guerin was a digital adviser to the office of the former New Zealand prime minister Bill English.

Topham Guerin told the Guardian it would not comment on “fundamentally inaccurate claims” made about its work with CTF Partners, but declined to say in which way the claims were inaccurate. It did not respond to further questions about its work with Crosby’s company or whether it had ever been involved in online Brexit campaigns.

The London office of CTF Partners is ultimately run by Sam Lyon, a former Boris Johnson spokesperson who helped run his 2012 mayoral election campaign, while one of those involved in running the pro-Brexit digital campaign is a former political adviser to Johnson. Canzini and CTF Partners did not respond to a request for comment.