The owner of Ladbrokes, Entain, has been accused of “dishonest” lobbying after it funded an operation mobilising people to complain to their MP about proposals to reform gambling laws.

The government last month unveiled plans for tighter regulation, including measures it said would make gambling safer but would also reduce revenue for brands such as Coral and PartyCasino, owned by Entain.

At the time, Entain’s chief executive, Jette Nygaard-Andersen, said the company welcomed “an important step towards having a robust regulatory framework that is fit for the digital age and creates a level playing field for all operators”.

But emails seen by the Guardian indicate that, despite supporting the white paper in public, Entain was funding a lobbying operation designed to water it down or overturn it.

Days after the white paper was published, an organisation called the Players’ Panel, which claims to represent the interests of ordinary gamblers, wrote to people who had signed up to receive information about its work. “The government has decided to limit when and how much you can bet,” said the email. “This is going to significantly impact your ability to bet responsibly.”

The Players’ Panel then urged the recipients to write to their MP opposing the reforms.

As the Guardian has previously revealed, the group is funded and managed by Entain. At no point in the emails did the group disclose this, although the company’s name can be found on the group’s website.

Members of the group who were invited to write to their MP were then provided with 10 letter templates, some targeted at individual elements of the government’s gambling white paper.

One template referred to “a massive infringement on my personal freedom” and suggested that the MP could take up the issue with the gambling minister, Lucy Frazer. “It isn’t fair, it isn’t right and it isn’t British,” another concluded.

Other templates ask MPs to intervene to stop specific proposals such as limits on online slot machine stakes, tougher affordability checks designed to prevent unsustainable losses and restrictions on “free” spins.

The templates describe the white paper as a “negative step” that would “do more harm than good”, apparently contradicting Entain’s public stance on the proposals.

Carolyn Harris, who chairs a cross-party parliamentary group on gambling harm, said the lobbying effort was “shameful”. “These emails reveal their true colours as they immediately try to undermine the proposals using covert and dishonest tactics.”

Lady Davidson, the former leader of the Scottish Conservatives, said: “Of course it’s legitimate for the public to lobby MPs on upcoming legislation.

“But for members of parliament – and members of the public – to be kept in the dark over which well-funded gambling firm is behind lobbying efforts such as template emails is pretty underhand. In fact, it stinks.”

A former leader of the Conservative party, Iain Duncan Smith, said the disritribution of email templates showed a “level of dishonesty”.

“At no stage do these emails point out that it’s a lobbying exercise by a company,” he added. “They’re trying to hide behind constituents rather than coming clean about their own self-interest.”

Entain refused to say how much of the Players’ Panel funding it provided and whether any of its staff were involved in writing the templates.

It said in a statement: “It is hugely important that everyday punters have an active say in the consultation process that has been launched as part of the Gambling Act review, and especially those elements of the review that could impact a recreational past-time [sic] that is enjoyed by millions of people across the country.

“We do not see any contradiction between our welcoming of the review and our encouragement of our customers to make their voices heard in what is an important and necessary debate.”

Entain added that members of the Players’ Panel, some of whom have written articles about gambling regulation on the group’s website, were unpaid volunteers who did not receive any benefit from the company.