Ajan, from Hungary, had been at the IWF since 1976, serving 24 years as general secretary and 20 as president.
“I offered the best of my life to our beloved sport,” the 81-year-old Ajan said in a statement posted on the IWF website.
“When health circumstances related to the pandemic allow, holding elections would enable a new generation to start work as soon as possible on ensuring a bright future for the sport we love.”
American Ursula Papandrea will continue to lead the sport’s governing body as acting president.
Ajan’s resignation might benefit the Thai Amateur Weightlifting Association (Tawa) in its planned appeal against the IWF’s ban for doping.
It is believed that the Hungarian does not see eye to eye with certain Thai officials particularly Maj Gen Intarat Yodbangtoey, an IWF vice president and former Tawa chief.
Earlier this month, the IWF, through the organisation-appointed Independent Member Federation Sanctions Panel (IMFSP), banned Thai athletes from taking part in the Tokyo Olympics regardless of the change of date, among other sanctions, following a doping scandal. (See story here).
The 2020 Tokyo Games have been postponed until next year due to the COVID-19 pandemic.
Tawa’s IWF membership has been suspended for three years, the governing body said.
Under the ruling, Thailand’s U18 weightlifters are prohibited from participating in international competitions for an additional five months following the next IWF event whenever it takes place.
All other Thai weightlifters are banned from participating in international competitions for an additional 11 months following the next IWF event whenever it takes place.
Thai weightlifters have already been suspended since March 7, 2019.
Reports in Thailand claim Ajan had a role in the sanctions and that his resignation may be good news for Tawa.
The ruling was a result of eight Thai weightlifters, including 2016 Rio Olympic champions Sukanya Srisurat and Sopita Tanasan, testing positive for banned substances at the 2018 world championships.
Tawa bosses insist they and their athletes are innocent and blame their Chinese coach for using pain-killing gel that contained banned substances without their knowledge. (See story here).
They have vowed to lodge an appeal with the Court of Arbitration for Sport (CAS) against the IWF’s “unfair ruling”.
In January, all Tawa board members, including its president Boossaba Yodbangtoey, resigned less than a month after allegations of doping by young weightlifters were made in a German TV programme.
In the documentary by ARD titled Lord of the Lifters, Thailand’s 2012 Olympic bronze medallist Rattikan (now Siripuch) Gulnoi was seen admitting to using steroids when she was a teenager.
Last month, Prachya Keeratinan was elected unopposed as Tawa president.
Weightlifting is Thailand’s most successful sport at the Olympics with five gold medals, followed by boxing with four.
After Ajan’s resignation, Papandrea said: “We can now begin the work of determining a fresh path towards achieving the full potential of our sport.”
Papandrea, a former international lifter for the United States, is the first woman to lead the IWF, which has existed under different names since 1920 and has had only two presidents since 1972 - Ajan and Austrian Gottfried Schoedl, who died this week aged 95.
Ajan has repeatedly denied allegations made in the ARD documentary.
The allegations, according to a document on the IWF website, were “primarily against” Ajan and concerned “financial irregularities, corruption, doping control distribution, doping sample manipulation, doping payment irregularities, doping activities in specific nations and nepotism”.
Ajan stepped aside as IWF president in the last week of January, initially for 90 days.
He said then that the allegations against him were “not supported by the relevant documentation or by people involved in the relevant decisions”.
Weightlifting has had problems with doping for decades and has been threatened by the IOC with expulsion from the Olympic Games.