Gloucester head coach Johan Ackermann accused Montpellier of illegal scrummaging after his team were beaten 30-27 in a thrilling European Champions Cup clash at Altrad Stadium.

The Cherry and Whites played the last 24 minutes with a man advantage after Montpellier lock Jacques du Plessis was sent off for a swinging arm on Gerbrandt Grobler.

It allowed Gloucester to come right back into the equation with second-half tries from Matt Banahan and Joe Simpson - but it was not enough for victory.

Ackermann felt Montpellier's scrum - which was dominant throughout - was based around illegal technique used by tighthead prop Levan Chilachava.

"In the scrums there was a grey area and I felt there was a lot of illegal stuff from Montpellier which was obviously missed. They got away with it," he said.

"I felt their tighthead was angling in. From where we sat he was never straight. If he's always angling in, then obviously the scrum is going to look dominant there and it's a pity it wasn't taken in by the officials.

"We tried to fix it and it got better in the second half, but the reality is they got away with things in the first half. It's not going to change the result."

Montpellier won 10 of their 11 scrums and their giant pack ultimately laid the platform for a narrow win.

First-half tries from Jan Serfontein, Caleb Timu and Nemani Nadolo put the hosts 24-10 up at the break with Callum Braley responsible for Gloucester's effort.

Du Plessis' red card gave Gloucester priceless momentum and Banahan and Simpson crossed as Billy Twelvetrees kicked two conversions and two penalties.

Ultimately it was still not enough for a win and Ackermann said he had no regrets about fielding a weakened side despite his team coming so close to victory.

"The changes were thoroughly thought through. We selected a team we thought would be enough to win," Ackermann said.

"We let ourselves down on execution, but it definitely wasn't down to a lack of effort. The players are disappointed, but the one thing I saw was unity on the field."

Back-to-back defeats mean Gloucester are bottom of Pool Five and Ackermann said: "It will be tough to qualify.

"We'll probably have to win all four games now and that's without looking at the other results. The club is proud to be part of this world-class competition and we're not happy we've lost."

Du Plessis' dismissal almost cost Montpellier the game but 15 points from the boot of Benoit Paillaugue ultimately proved crucial.

Wing Nadolo said: "It was a tough game. Gloucester bring that English style of play and they're a very structured side.

"They ran us off our feet at the end and I was fortunate to get a try and probably a bit unlucky not to get another one. We stuck in there and came away with the win.

"The red card could have been a turning point had we not worked a bit harder. It was disappointing obviously, but I thought we held our own. It was pretty tough out there."