Males and females of all ages will have to wear a weightlifting uniform when they weigh in, and any mention of the contentious word "undergarments" has been removed from the updated rules, which are effective immediately.

Nobody will be allowed to weigh in naked or bra-less, and there will now be an across-the-board allowance of 250 grammes for the uniform, which means any athlete who is over the weight limit for their category by 250g or less will be eligible to compete.

In other changes, video playback has been made compulsory at all continental championships and Olympic qualifiers, and flags have been banned from medal ceremonies at IWF competitions.

All three changes were welcomed by the IWF Athletes' Commission, which was unhappy about lack of consultation when the weigh-in rules were announced last November and came into force for the World Championships a month later.

There were complaints from female athletes at the European Championships in Armenia in April about lack of consistency in the rules, after they had been told to wear a bra for the weigh-in.

They had been allowed to weigh-in topless at the World Championships in Colombia in December and complained that compulsory wearing of a bra was unfair on women, because they weigh about 200g and no men wore them.

Britain's Zoe Smith said, "We are at a disadvantage compared with men because we were told we have to wear twice as much underwear at the weigh-in.

"The rules are not consistent - others have spoken about it here (at the European Championships) and we want consistency."

The problem was the interpretation of the word "undergarments" in the rules, which did not specify whether it meant one item of clothing or two.

Technical officials at the World Championships interpreted "undergarments" differently to those at the European Championships.

The simplified rules state merely that "athletes must be weighed in their weightlifting costume".

A typical lightweight singlet weighs about 140g but lighter versions will be available - and as there is no stipulation in the rules, athletes will be able to weigh in wearing an ultra-lightweight uniform, and swap it for a different one on the platform.

"We had a meeting and decided to approve the 250-grammes rule," said Athletes' Commission chair Forrester Osei.

"The main consideration has always been protecting young athletes and some of our vulnerable adult athletes.

"There are also a number of Technical Officials who have not been happy with the weigh-in procedures if some athletes have insisted on weighing bra-less.

"That cannot happen now and we believe it is the correct policy not to allow naked weigh-ins.

"Anybody who does not follow the rules will be told, 'You can’t compete'.

"We must make sure that we educate our athletes, their support personnel and member federations so that they know this.

"The new rules make things easier for athletes."

The changes became effective this week, two days after the European Junior Championships had started in Bucharest, Romania, where some athletes weighed in under the old rules and the rest wore a uniform to comply with the updated rules.

"They have all been very good about the changes," said Tina-Marie Bendix-Beiter, chair of the European Weightlifting Federation Technical Committee.

Bendix-Beiter also said that all athletes who weighed in within 250g of the limit, for example in the women’s 71kg category, would be logged as 71.00kg regardless of whether they were one gramme or 250g higher.

There could be queries about the procedure in all-weight competitions, which are used in some national championships and in new events such as street weightlifting, because they are scored by Sinclair points or Robi points, for which precise weights are needed.

"The important thing was getting the rule in place for the World Championships (in Saudi Arabia in September) and we can develop it from there," said Osei.

He said that a digital projection of the weight shown on the scales at weigh-ins would be visible to everybody at weigh-ins "to build trust between athletes and Technical Officials".

Osei welcomed the ban on flags on the podium, where digital versions of flags on a big screen were "what we want to see".

This was formal ratification of a decision announced in May by IWF president Mohamed Jalood after incidents this year and last year - a flag-burning in Armenia and a confrontation on the podium in Albania.

"This is a good rule, one that protects our athletes and our sport," said Osei.

"Sport is sport and politics is politics."

The video playback amendment came after a controversial decision at the Pan American Championships, an Olympic qualifier, in Argentina in March.

The American Mattie Rogers thought she had made a good lift only to be denied by the referees, and she was unable to challenge the decision because there was no video for the jury to review.

Video playback was already compulsory at all IWF World Championships across the age groups, at the Olympic Games and the Youth Olympic Games.

In one other amendment to the IWF’s TCRR (Technical and Competition Rules and Regulations), the maximum height of the stage above the referees' seating positions has changed from one metre to 80cm.