Yesterday Sunday Telegraph political editor Hennessy was named deputy director of comms for the party, reporting to Bob Roberts.
The hire of Hennessy, who is widely respected in the lobby and has nearly 30 years of journalism experience, drew plaudits.
George Pascoe-Watson, Portland Communications partner and former political editor at The Sun, praised the current Labour comms set-up but said a hire of Hennessy’s seniority was required.
"Paddy is a very heavyweight appointment for the role, and shows that Ed Miliband realises the comms set-up needs strengthening. That’s not a criticism of Bob Roberts, it’s a reflection of the need for more firepower in the age of constant communication. His biggest role will be in bringing message discipline across the party."
Hennessy’s experience at The Telegraph would also prove crucial, added Pascoe-Watson.
"It means he has strong relationships with Conservative Party figures, and a knowledge of the thinking among a number of its Cabinet ministers and advisers. That kind of top-notch intelligence is quite rare."
The appointment follows the Tories' hire of Tim Collins into a similar role in July.
With the 2015 election in sight both parties have sought to strengthen their communications offers, but the Tories were widely seen as on the front foot in their messaging over the summer.
Jim Dickson, director of public affairs at Four Communications, said: "Paddy is a key hire and helps redress the balance but they still have some way to go if you look at what the Tories have done recently.
"What Labour need is someone who can handle the field operations work, in terms of being able to convert the numbers in the way the Messina can and use that for both demographic and geographic targeting."
One government source pointed to Hennessy’s appointment helping the party "understand how the papers work inside out".
The source added: "Paddy knows the news and how to make it and that should help with some of the comms issues they’ve faced in recent months."
This included criticism of how the party was communicating by shadow health secretary Andy Burnham.
PRWeek understands that Labour is still planning to add to its in-house digital team, which is currently working with Blue State Digital.
Martin Frizell is executive director, media at Golin Harris and former GMTV executive producer.
He added that broadcasting skills should not be ignored, where he said the Tories were also "ahead of the game."
"Today’s hire still leaves a gaping hole of broadcast knowledge for Labour," he said, "and whether the lobby likes it or not, television is key in the race to Downing Street. Ed Miliband still has to convince the millions of undecided women in the UK that he’s worth a punt. Where and how he comes across in vision, the stories Labour can generate, the case studies they offer across the whole schedule, and not just news programmes, will be decisive."