Electoral rules currently allow political parties to invite voters to send postal ballot application forms (not the actual completed ballot papers) to political party offices rather than to the local authority conducting the election. As the website Skwawkbox says below, this would appear to be potentially fraught with the risk of facilitating fraudulent applications, but it is currently permitted.
However, political parties are not allowed to encourage voters to do this. In fact, the Postal Vote Code of Conduct instructs them to discourage it by making the preferred return address that of the official Electoral Returning Officer.
However, blogsite Skwawkbox:
Yet another Tory electoral breach – the SKWAWKBOX needs your help
gives an example where a local Tory office of a nearby authority (Somerset) gave its own address as its first option and that of the Electoral Returning Officer as the second option. With no address given for the ERO.
From Skwawkbox.
“A local resident wrote to Somerset County Council’s Strategic Manager of Governance and Risk about this breach and received this response:
“Thanks for sending a scan of the letter. Having studied the Code of conduct for campaigners in Great Britain and spoken to the Electoral Commission the letter should have the Electoral Services Office as the primary address for return of the form. The letter can include a secondary address.
Clearly this is not the case with the example that you sent through. Campaigners can receive completed forms and should then forward them to the Electoral Registration Officer’s address within two working days of receipt.
In the light of what you have sent through Pat Flaherty as County Returning Officer has raised this formally as an issue with the Conservative Party elections agent to point out what needs to happen under the requirements of the Code.”
As Skwawkbox says:
“This may seem like a small ‘technicality’, but it’s in such seemingly insignificant areas that space for election-tampering can exist – affecting the wellbeing of thousands and even millions of our citizens. … “
Skwawkbox is asking its readers to check for similar errors on party political websites to see what they say about arrangements for postal vote application forms and to let it know of any potential infringements of the Code of Conduct.
East Devon Watch 
I would assume that if a voter sends their completed request for a postal vote to the Conservative Party offices, there is nothing legally stopping them from opening the envelope (it is addressed to them after all) and, if the voter is known to vote for someone else to then lose the form. If this happened the first the voter would know would be when a postal vote doesn’t arrive and it is too late to request one.
That said, AFAIK there is no evidence of this happening, so it is perhaps only theoretical. Then again, even if no evidence has come to light it might already have happened.
LikeLike