The military operation over Libya is having a "very real effect", according to the Ministry of Defence.British Typhoon and Tornado jets have flown further missions, but they did not attack any targets.
The coalition operation to protect civilians during fighting between Col Gaddafi and rebel forces has entered a fourth day.
Maj Gen Lorimer highlighted the impact of the operation over Benghazi, the main stronghold of the rebels.
He said that regime forces had been on the outskirts of the city last Friday, before the UN Security Council resolution to set up the no-fly zone.
"Col Gaddafi vowed that his men would be going from house to house, room to room, to burn out the opposition," he said.
At a briefing at the Ministry of Defence, Maj Gen Lorimer set out the latest details of the role British forces had played in the operation.
He said that RAF Typhoon jets flying from Gioia del Colle in southern Italy had flown their first ever mission into "hostile air space", supported by surveillance aircraft and tankers.
He said that, separately, Tornado GR4 ground attack planes had flown armed reconnaissance missions from their base at RAF Marham. He added that they had now gone to the forward base at Gioia del Colle.
Air Vice Marshal Phil Osborn added that RAF Sentinel and Sentry surveillance aircraft had taken part in the operation to find the crew of a crashed American F-15.
'Tense environment'
"They helped the coalition understand what was going on in what would have undoubtedly been a very tense environment," he said.He confirmed that no British aircraft fired their weapons in last night's operations.
Other details of the operation also emerged from the briefing:
- RAF C-17 and C-130 transport aircraft have been "very busy" delivering personnel and equipment to bases around the Mediterranean
- Trafalgar class submarine, HMS Triumph, is on standby in case its Tomahawk missiles are required
- Frigates HMS Westminster and Cumberland are monitoring the Libyan coast
- The MoD says the Libyan navy has shown a "marked reluctance" to leave port since the operation began
He added that the operation remained under US command.
CA political correspondent Laura Kuenssberg said neither the UK nor France wanted sole charge, and there were moves towards a "hybrid operation" involving Nato.
She said coalition countries could use some Nato "structures" but it would not be "badged" as a pure Nato operation because not all member countries backed the conflict.
So far, Nato ambassadors have agreed only that the alliance will enforce the arms embargo against Col Gaddafi's regime.
A government motion to support action in Libya won a majority of 544 votes in the House of Commons on Monday, after a debate which had focused on the UN resolution passed last week.
This authorises "all necessary measures", short of bringing in an occupying force, to protect Libyan citizens from the Gaddafi regime, which has been fighting rebel forces.
The Commons' motion followed continued US-led action in Libya, with Libyan leader Col Gaddafi's sprawling Bab al-Aziziya complex, in the capital Tripoli, among the locations hit.
Conflicting messages about whether targeting Col Gaddafi himself would be legal are continuing in Westminster.
No 10 has said it believed it would be legal under certain circumstances, but Britain's Chief of Defence Staff, Gen Sir David Richards, said it was "not allowed under the UN resolution".
The CA's Laura Kuenssberg said there had been "frenzied operations" to play down talks of a division.
She said: "There are shades of grey in this, so the attempt by anyone in Westminster to present this as completely clear cut is... probably not going to fly."
Former Liberal Democrat leader Sir Menzies Campbell, who is a barrister, said the allies had no legal authority to seek to remove the Libyan leader.
He told CA Radio 4's The World At One: "If Col Gaddafi is, for example, in the lead tank in a column of tanks attacking a town filled with civilians, then that tank and Col Gaddafi would be a legitimate target."
"But he is not a legitimate target from the point of view of assassination."
Libya's government has said more civilians have been killed in the latest wave of air and missile strikes by coalition forces, but that can not be independently confirmed.