Boss of parent firm Frasers Group, Ashley was widely criticised after he told Sports Direct staff to head into work despite the government ordering all non-essential stores to close earlier this week.
The retailer had initially claimed that its position selling sporting and fitness equipment was "vital" during self-isolation to help stop the spread of coronavirus.
In an open letter Ashley said he was "deeply apologetic" over his initial response to the lockdown.
He eventually U-turned after pressure from MPs.
An open apology from our CEO Mike Ashley pic.twitter.com/q76uCq4btN— Sports Direct (@SportsDirectUK) March 27, 2020
He said: "In hindsight, our emails to the Government were ill-judged and poorly-timed, when they clearly had much greater pressures than ours to deal with."
He added: “On top of this, our communications to our employees and the public on this was poor.”
Ashley ends his letter with a commitment to support the NHS by offering his company's "entire fleet of lorries" for deliveries.
He said: "Outside of Frasers Group, I have offered our support to the NHS and we are poised and ready for when that offer is accepted, with our entire fleet of lorries at their disposal – to help deliver medical equipment and supplies.
"This offer is not limited to the NHS but all key workforces across the Government. We will help wherever possible."