No racing took place in Britain on Wednesday as the sport united to protest against proposed betting tax changes.

All four of the scheduled meetings were cancelled and rescheduled with participants of the sport downing tools for the day in a bid to urge the UK government not to raise the levels of taxation of betting.

Many of the sport's major participants and leaders were present at Westminster in London to show their support for the 'Axe the Racing Tax' campaign, with high-profile trainers, jockeys and MPs coming together as attempts to rally against the proposed tax changes.

An independent model commissioned by the BHA (British Horseracing Authority) has forecast a A$675 million loss in revenue over the next five years should the Treasury go ahead and raise the rate of tax on horserace betting from 15% to 21%, therefore moving it in line with the current level for online gaming and casino slots.

Jim Mullen, CEO of the Jockey Club, said: "What's being proposed here is a tax against horse race betting online and the industry just cannot afford that.

"What we are basically saying, in the event of that happening, then it will have a significant impact, not only in communities, but on the net tax revenue income on the government.

"We're just saying, stop and think through the details, look at those specifics and you will see that this doesn't make sense."

Champion jockey Oisin Murphy, Hollie Doyle and her husband Tom Marquand were among the jockeys standing outside of Westminster Abbey on Wednesday afternoon, while the BHA chair Lord Allen labelled the proposed tax increase as "nothing short of an existential threat for our sport."

Racing will resume on Thursday as normal, with Doncaster's four-day St Leger meeting.