Hi Sharon
I assume the door is marked as a fire exit on the inside, and as such should be available for use at all times that the premises are in use. Sometimes buildings have more exits than they may strictly need but if its signed as an exit it must be available for use and lead to a place of safety well clear of the building- ie the assembly point.
Has the Responsible person not carried out a risk assessment and identified this as a hazard?
Duties of responsible persons are set out in articles 8 to 22 but in relation to the obstructed exit the following may be being breached
Article 8 - duty to take general fire precautions to protect safety of "Relevant Persons"
Article 9- Duty to cary out a suitable and sufficient fire risk assessment, record the prescribed information if more than 5 employees, and review the risk assessment
ARTICLE 14 DUTY TO ENSURE EXIT ROUTES ARE KEPT CLEAR AT ALL TIMES
Employees may also be in breach of Article 23 - duty to take reasonable care for onself and for others and to co-operate with employer and to report any hazard,
Failure to comply with the order is an offence and may result in both enforcement action and prosecution.