You need a paper trail.
'Could you advise me of the current position with... including the timescales you have identified?'
'Thank you. I need to draw to your attention that the legal requirements (specific laws) are that ... must be completed within ... days of... Could you send me a revised timescale by ... , taking into account the statutory obligations...?'
'Thank you. However, this does not appear to take into account... Could we discuss this tomorrow at xpm?'
'Following our meeting on ....., I would like to clarify that you have ... and ... and will be making the following changes by and we will review this at ... intervals or sooner if necessary'
'Following our conversation on ... here are the links to .... where you will be able to access further information in order to resolve the issue with... If you require further support with this, please let me know by ... as the consequences of ... would result in [negative outcome for clients and organisation]'
'Thank you for your update today, where the revised timescale of ... was agreed in order to comply with .... and that you will be ...... by Tuesday 15th. If there are any problems or you need input from ...., please let me know by 1pm Thursday 10th and I'll be able to ....'
[4.40pm on 15th] 'Good afternoon, just checking in to make sure that .... is progressing as agreed and whether you require me to arrange for input from .... to be able to complete stage 22b/4/d.1234 by Tuesday 15th'
'Thank you for your update. I am concerned that ... has not yet been taken into account. I have contacted ... to ask whether they are able to offer their expertise/experience in...'
'Good morning, ... will be available on .... for you to discuss ... Could you contact them and confirm a meeting, letting me know the outcome by ...?'
It's all a huge arse covering expedition, unfortunately, but documenting all the times that you have contacted them, asked questions, checked for progress, provided information or sources for them to obtain the information and any shitty messages received in response will give HR enough to deal with any grievances raised against you when they realise the shit is about to hit the fan, along with giving HR and the Union enough evidence to be able to say 'Well, all the processes were followed, but x happened/didn't happen, which resulted in y, which the employee was made aware on multiple occasions', which leads to unions saying 'it's less than 50/50, so you don't get legal cover to take this further, we're better off discussing an agreed exit and reference than claiming discrimination or victimisation, and even then, you'll be lucky to get an agreed reference'.