Referees' chief Mike Riley admitted on Thursday that four VAR mistakes have been made in the Premier League this season.

Riley addressed the controversial issue of VAR use in the Premier League at a meeting of top-flight club chairman in London.

The VAR blunders included Fabian Schar's equalizer for Newcastle against Watford, which should have been disallowed for a handball by Isaac Hayden, and Leicester midfielder Youri Tielemans avoiding a red card for an apparent stamp on Bournemouth's Callum Wilson.

The other two errors were the decision not to award Manchester City a penalty when Bournemouth's Jefferson Lerma fouled David Silva and West Ham not getting a spot-kick after Sebastien Haller was brought down by Norwich's Tom Trybull.

Riley, the managing director of the elite refereeing body, said the Silva, Haller and Tielemans incidents were indicative of the high bar the Premier League has set for overturning the decisions of the on-field referee.

But he conceded the "clear and obvious" bar had been reached in each of these cases.

"If you look at the four match rounds 227 incidents have been checked," Riley told Sky Sports News.

"Out of that we've changed six decisions, (and) we think we should have changed 10 in total.

"That gives you the scale of where VAR can help and add value to the game. But it also demonstrates that this is still about refereeing a game of Premier League football on the pitch."

It is also understood that clubs discussed the length of the summer transfer window at Thursday's meeting.

Clubs voted two years ago to move deadline day, previously at the end of August, to a date before the season began.

But with no uniformity of deadlines across Europe, some managers have urged a rethink because players can still be lost to clubs abroad after the Premier League window closes.

The matter was raised at the meeting but no decisions were made and it will be discussed again in November.