Paul Lambert may be feeling the pressure as his side slid into the Premier League relegation zone, but questions about the Aston Villa manager's immediate future were conveniently overshadowed by the latest in a series of "diving" controversies. Discussion about the safety of Lambert's tenure at Villa Park will have to wait for another day.

Instead, Lambert chose to criticise Mark Halsey, the referee, for awarding Southampton a penalty that clearly was not in the 34th minute. Jay Rodriguez, the Southampton forward, fell in the home area, as Enda Stevens, the Villa left-back, prepared to challenge him.

There was no contact – video replays confirmed that – but Halsey, a late replacement for flu victim Chris Foy, pointed to the spot. Rickie Lambert converted the 31st penalty of his career, from 31 attempts, and Villa were condemned to a place in the bottom three.

"It was absolutely not a penalty," Lambert said. "I've chatted with Mark and he was adamant, 100%, that it was. But he's guessed, he's got it wrong and he will be embarrassed when he sees it. Referees have got to try to get the big decisions right. You just can't guess these things. I'm not going to get involved in calling anyone a cheat. But you can't go down if you haven't been touched."

Nigel Adkins, the Southampton manager, concurred that it was not a spot kick but absolved Rodriguez from having dived. The player was trying to avoid a collision, Adkins claimed. "There was no contact," he said. "Jay was moving out of the way. Otherwise, there would have been contact.

"The challenge came in and Jay has evaded it. The referee has a decision to make and he gave a penalty. I don't think Jay even appealed for one. I don't advocate diving but we've not been given seven or eight penalties this season so maybe what goes around comes around."

When told of Adkins's somewhat convoluted explanation, Lambert said: "Give me about four days to work that out. I just don't know how to answer."

Lambert admitted to two sleepless nights after his side had succumbed 3-1 to Bradford City in the first leg of their Capital One Cup semi-final last Tuesday. He might not sleep for a week after this latest setback in the rapidly accelerating fall and fall of Villa.

Defeat against Southampton, their fellow relegation strugglers, at a numbingly cold Villa Park took Villa into the coldest extremities of the Premier League. If the loss was not as embarrassing as that at Valley Parade, against League Two opponents, it was damning nonetheless.

Even a late rally, during which Nathan Baker nodded against the Southampton crossbar and Christian Benteke missed a host of chances, failed to mask Villa's obvious frailties. They have scored one goal in their past six home matches and are plummeting faster than the temperatures in the west Midlands.

Where do they go from here? Well, they could redress the balance when they take on Bradford in their second leg on 22 January. Wembley still beckons. And perhaps also via a second route, with an FA Cup fourth-round tie to come with Millwall, of the Championship, on 25 January.

Yet if their cup runs offer a welcoming and intermittent respite, it is in the bread-and-butter of the league that they need to improve. And drastically. And soon. With only Queens Park Rangers and Reading below, Villa are an accident waiting to happen. Already, it would appear, they are in a sickly skid, utterly out of control. Villa offered little in the first half, with Benteke ploughing a lone, isolated furrow. But after Lambert had coolly despatched the contentious spot kick, which separated the sides at half-time, Villa improved. Andreas Weimann shot weakly at Artur Boruc, the Southampton goalkeeper; then after Boruc had saved smartly from Stevens's piledriver, Benteke volleyed over the loose ball. Charles N'Zogbia also had a chance but could not muster enough power to trouble Boruc.

On a rare break, Southampton could have increased their lead, but Puncheon's long-range effort crashed against the crossbar. Cue the late Villa surge. But Benteke's radar continued to act up and Lady Luck again deserted Villa. No more "Zzzzzz" for Lambert for some time yet.