The decision was also taken, by a vote of 126 to 25, to increase the course length for all Para-rowing events from 1,000 to 2,000 metres, bringing it up to parity with able-bodied rowing.

The vote on the Olympic boat classes, despite being narrower than many expected, will come as a huge relief to the Federation's President Jean-Christophe Rolland and ex-President Denis Oswald.

They had starkly warned delegates on the previous day that the International Olympic Committee (IOC) would be almost certain to reject the alternative proposal put forward by Australia, Switzerland, China and Denmark, that would have given lightweight events four of the 14 places currently available.

In order to gain gender equality, one of the key requirements for future Olympic event programmes, FISA proposed cutting the men's lightweight sweep rowing four (LM4-) and adding a women’s heavyweight four, leaving only two lightweight events in the Games programme - the men's and women's double sculls.

This proposal, due to come into effect by the Tokyo 2020 Olympic Games, will now be forwarded to the IOC Executive Committee which will make a final decision in July.

The alternative proposal was to replace the men’s coxless four (M4-) rather than the LM4- and to bring in a lightweight women’s coxless four (LW4-).

But Oswald, the Swiss IOC member who is currently working closely with the IOC President Thomas Bach as he heads one of the Commissions established to investigate Russian doping evidence, told delegates on the opening day that Bach had privately told him any proposal to increase lightweight rowing at the Olympics had "no chance".

As part of a review of the Olympic sports programme which was part of Bach's Agenda 2020 initiative, the IOC decided against including weight classes at the Games apart from in combat sports and weightlifting.

Rolland told delegates that when he, Oswald and FISA’s executive director Matt Smith had begun talking to senior IOC figures following that decision, the starting point was 'no more lightweights'. 

"Zero lightweights - and don’t tell me that they don’t know about the sport, they know exactly about the sport," Rolland said.

"So this is the situation."

Earlier in the week, Britain’s Olympic gold and silver medallist in the lightweight men’s double sculls, Mark Hunter, said that rowing was being "strangled by the IOC to do what they want".

Speaking of the alternative proposal, which would have offered lightweight doubles and fours for men and women, Oswald, responsible for getting lightweight classes onto the Olympic programme in 1996, added: "If I were the one to decide, I would buy it immediately. 

"Unfortunately I am not the one to decide. 

"I know it would be good for our sport, I know. 

"But if we are rejected by the IOC Executive Board, what do we do after?

"I am disappointed as well. 

"It would be fantastic to have four events for lightweights at the Olympics.

"But it’s just not realistic, not possible, unfortunately.

"Two years ago the Olympic Programme Commission had decided to eliminate completely the lightweights, and thanks to the work done by Jean-Christophe and our executive director Matt Smith they have been able to achieve something that will keep at least two lightweight events, one for women, one for men, under the principle of universality.

"But it is an exception to what the IOC have normally decided and was prepared to do.

"So we cannot take the risk to lose everything."

On the subject of the Para-rowing course change, a World Rowing statement added: "This will be the case at all World Rowing events as well as the Paralympic Games, and makes for better integration of Para-rowing into the regatta programmes."

In other changes, either males or females may serve as coxswains, regardless of whether the boat is a women’s crew or a men’s crew. 

The minimum weight for a coxswain is now 55 kilograms and the maximum amount of deadweight is 15kg.

American Samoa became FISA’s 151st member federation.