By Pritha Sarkar

LONDON, June 30 (Reuters) - Venus Williams accused Wimbledon officials of discriminating against its women champions and wants "equality" when it comes to scheduling matches on its two biggest showcourts.

After two days of rain created a backlog of matches, the five-times Wimbledon champion was sent to the 782-seater Court 18 on Thursday, an arena once labelled "a parking lot" by former world number one Jelena Jankovic.

While in 2008 Jankovic had fumed she "needed a helicopter" to reach the smallest of Wimbledon's six showcourts, Williams kept smiling as she delivered her message to the most famous of tennis tournaments.

"I'm not so much into disrespect. I'm willing to play anywhere, any time," the oldest player in the women's draw said after her second-round win over Greek qualifier Maria Sakkari.

"All players should have to play outside. There shouldn't be exceptions or any inequality to it.

"It's not the ideal schedule for the women. We'd like to see equal amount of matches (on the main showcourts). We don't want more, just the same amount, that's all."

Williams and her sister Serena own 11 Wimbledon singles titles between them but over the years the duo have found themselves playing away from the two main showcourts.

In contrast, the men's Big Four of Novak Djokovic, Roger Federer, Rafael Nadal and Andy Murray will have to think back a number of years to remember the last time they were exiled from the two main arenas.

Martina Navratilova, winner of 18 grand slam singles titles, tweeted "it stinks" after she spotted Thursday's order of play.

"To make it crystal clear... I just want equality for men's and women's matches. That's what I'm unhappy about," added eighth seed Venus.

"The All England Club has to have a culture where they want to have equality. They need to want to pursue that."

Except for Tuesday, when defending women's champion Serena opened Centre Court proceedings on what is traditionally known as Ladies' Day, Wimbledon has scheduled two men's and one women's match on the main 15,000 capacity arena.

Over on Court One, there has been an even split of men's and women's matches over the first four days this year.

Home favourite Andy Murray, the 2013 champion, admitted he was "a little bit" surprised to see Venus on Court 18 but defended the scheduling.

"It's not like that's a bad court... 18 is a good court," Murray said after easily beating Lu Yen-hsun on Centre Court.

"They do a pretty good job of trying to put the best matches for the fans... rather than it just being the big names that play on the big courts."

Asked if she could imagine a five-times male champion being on an outside court, Venus added: "I haven't seen that in the scheduling yet."

(Reporting by Pritha Sarkar, editing by Clare Lovell) ((pritha.sarkar@thomsonreuters.com; +44 20 7542 7933; Reuters Messaging: pritha.sarkar.thomsonreuters.com@reuters.net;))