P&O Ferries has “one last opportunity” to U-turn on the sacking of 800 crew before a package of legal measures is brought in to force its hand, the government has warned. The transport secretary, Grant Shapps, is expected to unveil an eight-point plan on Wednesday that will include tightening employment laws for ship operators in UK waters, including on minimum pay and consulting on redundancies. P&O Ferries said it welcomed the move, which would mean “a level playing field”, after the government allowed Irish Ferries to start operating the Dover-Calais route using low-paid agency staff last year. Shapps told P&O it must lift this Thursday’s deadline for the sacked employees to sign redundancy and non-disclosure agreements. Writing to the firm’s chief executive, Peter Hebblethwaite, on Monday, Shapps spelled out his intention to legislate, informing him that P&O Ferries would be “left with little choice but to reverse your decision in any case”. According to P&O, 430 of the sacked crew have fully accepted the redundancy offer and only 29 have not yet indicated that they will do so. On Monday evening the Maritime and Coastguard Agency confirmed it had detained a second P&O ferry after it failed safety checks. The Pride of Kent vessel follows the European Causeway, which was held at the port of Larne in Northern Ireland on Saturday after being declared “unfit to sail”. Shapps had earlier warned Hebblethwaite that his position as chief executive and a director had “become untenable”. In the letter, which Shapps posted on Twitter, he said a package of measures would “block the outcome that P&O Ferries has pursued, including paying less than the minimum wage”. It came as the Commons transport and business committees wrote a joint letter to Shapps demanding that Hebblethwaite be struck off as a company director as “not a fit and proper person” after he “flaunted his contempt for the law” at last week’s hearings into the mass sackings on 17 March across P&O Ferries’ UK fleet. Hebblethwaite admitted the firm broke the law by dismissing the workers without consultation, amid plans to bring in cheaper agency crew at below minimum wages, saying: “There’s absolutely no doubt we were required to consult with the unions. We chose not to do that.” The committees’ chairs, Huw Merriman and Darren Jones, said the government should prosecute P&O Ferries and remove its licence to operate in the UK for failing to consult on redundancies. The MPs urged the government to impose the “unlimited fine” it has threatened if it decides P&O Ferries has broken laws that require it to notify the relevant authorities of impending layoffs. They said ministers should “prioritise the wellbeing of those 800 seafarers”. Documents published by the committees show that P&O Ferries’ Jersey office sent Insolvency Service forms on 17 March – the day of the sackings, rather than at the required 30-45 days’ notice – to the relevant flag state authorities of the ships in Bermuda, Cyprus and the Bahamas. The forms spell out the legal duty to give notice, but also state: “If it is not reasonably practicable for you to comply with the minimum notification periods, you must make every effort do so as far as you are able. You must give reasons why you could not provide the information on time.” The P&O Ferries local agency director wrote on the form that no notice was given because: “To minimise disruption to the vital services we run on major sea routes, it was essential for the business to carry out the restructure as quickly and efficiently as possible.” Unions were meeting with the two other large ferry operators from UK ports, DFDS and Stena Line, and government officials on Monday to discuss the crisis and alternative provision of services. The RMT general secretary, Mick Lynch, said: “The sacked workers have to be reinstated and we need regulation and legislation to secure UK-based seafarers’ jobs and agreed contracts of employment.” Action from Shapps to tackle pay and conditions would contrast starkly with his actions of last year, when repeated warnings from unions over similar labour practices on Irish Ferries were ignored after the firm started operating services on the Dover-Calais route. The RMT union highlighted that agency staff recruited abroad and paid less than the minimum wage were now employed “and that the contagion will spread and more local seafarer jobs will go”. In August, RMT general secretary Mick Lynch said the government was “rolling out the red carpet” for Irish Ferries. Irish Ferries was also mentioned as a key concern to Shapps by P&O Ferries’ owner, DP World, in a meeting in Dubai last November. DP World’s chief executive, Sultan Ahmed bin Sulayem, told Shapps: “In respect of our ferry business, there’s a new low-cost competitor from Irish Ferries. This poses challenges in respect of P&O’s operations.” Shapps told him he was aware of the issues and recognised the need to make commercial decisions. P&O said it “fully welcomed the government’s commitment to increasing the minimum wage for all seafarers working in British waters”. A spokesperson said: “From the outset we have called for a level playing field when it comes to pay and conditions on British ferry routes.” It said its change was to get a “fully flexible crewing model”, with the predicted savings understood to be largely from not paying staff when they are not on board, in contrast to full-time employees. P&O sailings from Dover to Calais have been cancelled up to this Thursday and those between Larne in Northern Ireland and Cairnryan in Scotland remain suspended. The Hull-Rotterdam service was cancelled but Liverpool-Dublin sailings were going ahead on Monday.