Consider the following scenario:

Sunrise UK is a subsidiary of Sunrise Coffee Ltd., a company operating in 60 countries around the world. Sunrise UK employs 7000 staff across 600 coffee shops. Since it began operating in the UK, Sunrise UK has generated over 2billion in revenues and has paid 6.5million in UK corporation tax.

Sunrise UK receives tax consultancy services from a Big Four accountancy firm who have advised Sunrise UK to follow an aggressive tax management and tax avoidance plan that includes making use of tax reliefs and structuring transactions in a way that minimises the amount of corporation tax paid in the UK. Sunrise UK makes use of transfer pricing in order to shift profits to a subsidiary in a small European country, where corporation tax rates are lower than in the UK.

Earlier this year, customers boycotted Sunrise UK after their tax avoidance practices were made public in a high-profile report by a leading newspaper. Sales declined for the first time in 10 years and Sunrise UK closed 10 of its stores.

In response, the managing director of Sunrise UK said: "We pride ourselves on our ethical conduct and we are disappointed that customers have lost trust in Sunrise UK. What people may not realise is that we pay millions of pounds in employer's National Insurance contributions every year. We are proud to have created thousands of jobs in the UK and we are a large contributor to the UK economy. While we do not comment on our tax planning practices publicly, I can assure you that, on the advice of our accountants, we fully comply with the law in all countries that we operate in. Sunrise UK pays its fair share of taxation".

Critically discuss the ethical issues in the above case and critically evaluate the extent to which Sunrise UK's tax payment and avoidance practices are ethical. Refer to relevant ethical theories and academic literature within the answer. The maximum length of answer is one thousand and five hundred words.