Chelsea boss Frank Lampard has called for an "open conversation" on VAR after another weekend of controversy in the Premier League as he prepares his team to face Ajax in the Champions League.

Chelsea, who are fourth in the Premier League, endured a nervy end to their match against Watford on Saturday after their 2-0 lead was halved by a VAR-awarded penalty converted by Gerard Deulofeu.

VAR also confirmed an offside decision against Liverpool's Roberto Firmino during their 2-1 win at Aston Villa. The forward was flagged because his armpit "was marginally ahead of the last Villa defender".

Lampard, speaking ahead of his side's game against the Dutch champions at Stamford Bridge on Tuesday, said tweaks needed to be made over the use of the technology.

"I think the use of the screen on the side of the pitch can be a help because we've seen this weekend in the Premier League decisions that firstly they've taken a long time to get to, which seems to bring in the fact that there's an element of doubt," he said.

The lack of use of pitchside monitors by referees has been criticised after numerous controversial decisions in the first few months of the season.

"It just feels at the minute in the Premier League, obviously there are things that aren't right with it. I think that's pretty much universally agreed at this point," said Lampard.

Copyright Agence France-Presse, 2019