Engineers at Aston Martin have become "extremely demoralised" after new team owner Lawrence Stroll's fast-track plan for a competitive car backfired.

That is the view of former F1 team boss Colin Kolles, who has been firing barbs at both Stroll and Aston Martin shareholder Toto Wolff recently.

For instance, he said Mercedes boss Wolff is billionaire Stroll's "lap dog", and accused Aston Martin of only signing Sebastian Vettel in order to make Lance Stroll look better.

Now, he has told Sport1 that Lawrence Stroll overruled the Silverstone based team's technical strategy by forcing the 'pink Mercedes' on them last year.

"In the past, the engineers were allowed to develop themselves there. They had little budget, they were very young and efficient, very motivated and in some cases also very innovative," said Kolles.

"Since Stroll has been in charge, things have changed. And I mean everything."

The biggest of those changes was, according to former HRT and Force India boss Kolles, ordering the "almost 1:1 copy" of the title-winning 2019 Mercedes car be built.

"The engineers actually wanted to build a different car - one with a heavily sloping rear like the Red Bull - because the team had made its cars according to this philosophy for years," he alleged.

"But Stroll only wanted a copy of the Mercedes because that it seemed like the easiest way for him to achieve his goals. It is my way or no way - that's Stroll's mentality.

"He bought everything from Wolff," Kolles said.

When the aerodynamic rules then changed for 2021, the teams most affected were Mercedes and Aston Martin - but only Mercedes was able to rapidly react and improve.

As for Aston Martin, "the engineers can't do anything with a car they didn't want at all", Kolles insists.

"They are now extremely demoralised and hanging in the air. There is a lot of displeasure in that team now."