Is using a company name infringement?

A rival business has accused a client of mine of infringing its trade mark. It is not a registered trade mark. Nor is the business registered as a limited company.

The mark in question describes the location and nature of the business. I would say it was generic and descriptive. For SEO purposes my client has a web page with this title; as it describes a term which people may search for looking for a company doing business in this area for that particular type of work.

In no way is it suggested that this my client's website is to be confused with his. Since the first threat of legal action we have even added a disclaimer to that effect.

My company has since been threatened with legal action regarding this, but I don't think there is anything wrong with it. Do I need to do anything about this?

Alasdair Taylor's answer to Is using a company name infringement? (36832308)

Answer to the question: 

To properly answer this question, I would need to know what the trade mark is, how the trade mark and the allegedly infringing mark have been used, and all the circumstances around such use.

That said, if all the facts are as stated in your question and you are concerned about English law actions, I think the rival business would struggle to put together a robust passing off claim ("passing off" is the tort that best approximates unregistered trade mark infringement in English law).