Mads Ostberg and M-Sport WRC team at odds over poor Argentina pace

Ostberg finished the South American event in fifth place, almost five minutes behind winner Hayden Paddon.

Unable to travel to the event following an operation on his ankle, Wilson was watching from Britain and was not pleased with what he saw.

"Mads is still not where we would expect him to be," said Wilson.

"He has set some encouraging splits, but his overall stage times are a long way off what we wanted and we need to understand why he has been unable to match the speed of his rivals, or his fellow Fiesta driver Ott Tanak."

Ostberg defended his position and pointed to a lack of engine development from the team as well as an intermittent gearshift problem as causes for the apparent time loss.

"The engine and gearbox need work," said Ostberg.

"Sometimes, the gear is not going down when we go to the corner and when this is happening, you have to change your style to be less aggressive.

We need more pressure from the pump in the [gear] change system.

"We are behind with the engine. I understand it's difficult for Malcolm, but we have to face facts - the manufacturers are upgrading the engines and we need to do the same.

"I want to work with the team, we have to do something.

"I will talk to Malcolm after this rally. We talked after Mexico and we understood some things then."

Asked about the comparison with Tanak, who drives a DMACK-shod independent Fiesta, Ostberg argued that the Estonian is benefiting from better road positions as he is lower down the championship standings.

"It's not such a fair comparison with the cars behind me," Ostberg said.

"They have grip - they are driving on Tarmac compared with what I am driving on."