London - England's Stuart Broad has risked disciplinary action after appearing to question the legitimacy of Pakistan spinner Saeed Ajmal's action.
Ajmal is currently playing for English county Worcestershire.
He took 13 wickets in the Midlands side's recent County Championship win over Essex, including a career-best seven for 19 in the second innings.
That prompted former England captain Michael Vaughan to post a still photograph of Ajmal bowling during that match on Twitter with the caption: "You are allowed 15 degrees of flex in your delivery swing.... #justsaying."
Broad, currently out with a knee injury, replied by commenting: "This has to be a fake photo?!".
He then added in a subsequent tweet: "Bowlers can bowl very differently in a lab while being tested compared to needing wickets in the middle."
As an England centrally contracted player Broad can be penalised by the England and Wales Cricket Board (ECB) if he is found to have made derogatory comments about his fellow professionals.
Following the controversy surrounding former Sri Lanka off-spinner Muttiah Muralitharan's unorthodox action, the International Cricket Council ruled bowlers could straighten their arm in delivery by up to 15 degrees.
Ajmal's action has undergone extensive testing and been passed by the ICC.
However, English cricket has long been suspicious of 'mystery' spin and innovations such as the 'doosra' (other one) whereby an off-spinner bowls a delivery that turns away, rather than towards, a right-handed batsman.
Regarded as one of the best spinners of modern times, the 36-year-old Ajmal has so far played 33 Tests, 110 one-day internationals and 63 Twenty20 matches.
He took 24 wickets in helping Pakistan rout then-world Test number one England 3-0 in their series in the United Arab Emirates in 2012.