It's squeaky bum time on the Labour benches.

There's no hiding the fact that polls showing the Conservatives back ahead have seriously rattled Ed Miliband's party.

Although never truly loved by his MPs, Labour have been surprisingly loyal to their leader over the past four years.

They may not have been convinced by his plans for 'one nation Britain' or 'predistribution' but they have tolerated them as long as the polls have continued to show Labour ahead.

That has clearly now changed. Labour backbenchers were visibly grim-faced, tight-lipped and arms-crossed today as Miliband returned to the chamber.

He began by questioning Cameron's inaction on Pfizer 's takeover bid of AstraZeneca. There was little wrong in his line of questioning.

But there was an almost tangible hollowness to Miliband's words. Like a pea rattling around inside an empty pod. And Cameron knew it.

The prime minister's approach to prime minister's questions has never been pretty. He long ago gave up any pretence of trying to answer Miliband's questions.

Nor is it enthralling. There can be few people tuning in to BBC Two at lunchtime who haven't been tempted to hurl their egg mayonnaise sandwich at the screen after Cameron's umpteenth reference to his "long term economic plan".

But it is, in it's own way, effective. Lynton Crosby's strategy of making his candidates repeat a few stock phrases until the public become numbed into submission is an ugly thing to behold. But it also works.

It is an almost impossible thing to come up against. No matter what Miliband asks, Cameron answers with the same few production-line phrases.

Today Miliband repeatedly asked about the intricacies of the AstraZeneca deal and Cameron repeatedly answered about wanting to "get stuck in". Today Miliband repeatedly asked about projected job losses and Cameron repeatedly answered about Miliband "playing politics".

Like Labour's dreadful four-word election slogan, Cameron's slogans are often meaningless. What, after all, does "getting stuck in" actually mean? But the cumulative effect can be powerful. 

No casual viewer is likely to remember Miliband's detailed questioning about takeovers, but they may well remember Cameron's reply that "the country is getting stronger while he (Miliband) is getting weaker."

Labour MPs certainly looked like they will remember it.

In good times, Labour can afford to shrug this kind of stuff off. In the long summer of Ed Miliband's leadership, the occasional poor performance at PMQs could be forgotten.

But winter is drawing in for Miliband and his troops are restless. The next few months could be interesting times for the Labour leader.