The main lobby group for the UK gambling industry has been accused of making inaccurate statements relating to the regulation of the £10bn-a-year sector the day before its boss appears before a parliamentary committee.

Michael Dugher, the chief executive of the Betting & Gaming Council (BGC), is to be question by MPs on the select committee for culture, media and sport on Tuesday as part of a review of government proposals to improve gambling regulation.

On Monday afternoon, the Liberal Democrat peer Lord Foster wrote to members of the committee to raise concerns about the BGC’s reliability.

In the letter, shared with the Guardian, Foster referred to a BGC press release about a report it had commissioned that pointed to a spike in the use of illegal betting sites between November and December 2022, during the World Cup in Qatar.

In the press release, the lobby group said the report showed that punters could be driven into the arms of illegitimate gambling operators if government regulation of the sector went too far.

However, the full report, which was written by the gambling analysis firm Yield Sec, was never published. A copy obtained by the Guardian showed the report described the overall penetration of the parallel market as “low”, despite the rise, and that it accounted for as little as 1% of overall UK gambling spend.

Speaking after the press release was issued in January, Dugher said the report showed the government should beware of imposing “blanket intrusive affordability checks”, referring to proposed mandatory tests to check gamblers can cope with their losses. The report did not mention affordability checks as a cause of parallel market gambling.

The majority of respondents to a survey commissioned by the Racing Post said people would turn to illicit sites if affordability checks were introduced.

Foster told MPs on the committee he did not think the BGC had been “fully accurate” in its representation of the report, or the scale of the parallel market.

He said: “The solution to addressing the black market is to introduce proper enforcement to disrupt the operations of these sites […] rather than abandoning much needed additional regulation of the gambling industry.”

Foster also raised concerns about “other instances when the BGC has not been entirely accurate” with regard to its position on regulations.

In December 2022, Dugher tweeted that the lobby group had “fully and publicly supported” a ban on gambling with credit cards.

However, a Gambling Commission paper published in 2020 said “none” of the online gambling companies had supported such a measure during the consultation stage.

The BGC has also repeatedly said a voluntary industry ban on advertising during sport shown on television TV reduced the volume of gambling adverts seen by children by 97%. In fact, the figure was 70%.

The higher number referred only to the limited time period covered by the voluntary ban and only to television, caveats the BGC failed to make clear on several occasions.

In April this year, after the government said it was considering a mandatory levy on gambling firms to fund addiction research, education and treatment, the BGC said its members would “welcome” such a move.

However, Dugher had written in May 2022 it would be a “big step backwards” for tackling gambling-related harm.

In a statement, the BGC said it had “introduced scores of new safer betting and gaming measures, including ensuring our members devote 20% of all TV and radio advertising to safer gambling messaging – backed by our groundbreaking Take Time to Think campaign.

“The Yield Sec study was commissioned to analyse the scale of the growing, unsafe, unregulated gambling black market online and its findings were accurately reported.”