Robn Frijns has confirmed that a lack of sponsorship backing has forced him to end his involvement with the 2013 GP2 Series after five rounds.

"So that was it then. No money no drive," Frijns posted on Twitter on Wednesday. "Winning championships is not enough these days! Good luck for all the GP2 boys!"

The reigning Formula Renault 3.5 champion is also Sauber F1's test and development driver, and it was thought that the Swiss team was keen for Frijns to be involved in GP2 to keep him 'race fit' while carrying out his test duties.

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However the team is experiencing financial problems of its own, with a bail-out from a Russian group of investors not expected to ease their situation until the end of August at the earliest. In any event, the new backers will have their own ideas about what and on who the new influx of cash is spent on, and it seems that Frijns is not on the list of likely beneficiaries.

Frijns took part in GP2 testing over the winter before finally taking up a race seat at the new Hilmer Motorsports team for the second round of the 2013 season at Bahrain. He had a brilliant follow-up outing at Barcelona which saw him win the feature race and come second in the sprint, and overall he's amassed 45 points putting him in ninth place in the drivers championship.

His place in the #22 car will be taken by Britain's Adrian Quaife-Hobbs who is currently the reigning AutoGP World Series champion. Quaife-Hobbs has been driving for another of GP2's new teams, Manor MP Motorsport, and is in 16th place with 23 points. His best result so far was as runner-up in the Monaco sprint race in May.

With Quaife-Hobbs' move to Hilmer only being announced on Wednesday evening, that gave MP Motorsport little time to find a substitute driver ahead of this weekend's round at the Hungaroring, which gets underway on Friday with morning practice and afternoon qualifying.

In the circumstances, the Dutch team has opted for a safe and experienced pair of hands by calling up Spain's Dani Clos, a proven talent with three seasons in GP2 under his belt together with a two-round appearance for Barwa Addax in 2012 while he was also serving as test driver for the now-defunct HRT F1 team.

"We're delighted to welcome Dani to the team, he's a fantastic driver and has achieved a lot in his career so far", said MP Motorsport team principal Sander Dorsman, "The experience he brings to MP Motorsport will be priceless, he's won in GP2 and has tested in F1. We're all really looking forward to working with him for the first time in Hungary this weekend."

Another change in the GP2 line-up for Budapest was announced on Wednesday, with Ricardo Teixeira returning to Trident Racing in place of Kevin Ceccon. (See separate story.)