Yes, for Intra Company Transfer Work Permits ICT, you need 6 months.
please read
Intra Company Transfers (ICT)
This category is for employees of multinational companies who are transferring to a skilled post in a UK-based branch of the company.
The post must require an established employee who has company knowledge and experience that is specifically required in order to carry out the duties and functions of the post on offer and which could not be provided by a resident worker. (If this knowledge and experience is not essential for the post, we may require that the application be considered under another Tier 1 category (if applicable) or against Tier 2 criteria.)
You should supply information on the particular knowledge and experience the person has gained as an employee of the overseas company. You should explain why this knowledge and experience is essential in order to carry out the duties and responsibilities of the post.
If the person will not be working at the address of the employer given in the application form, you should explain why their specialist company knowledge and experience is needed at the working address.
The transferring employee should have at least six months experience working for the overseas company.
To qualify as an ICT, the UK company must have a direct link with the overseas company by common ownership (one company owns the other, or both must be part of a group of companies controlled by the same parent or holding company). If a person owns shares in two or more companies this will not in itself form the basis for us to consider an application under the ICT category.
Please send us supporting documents to confirm the link between the overseas company and your organisation if you have not done so in a previous application. If you are using the e-mail application form, you can scan in this information as an attachment. However, we reserve the right to request originals if we deem it necessary.
The UK is party to a number of Europe Agreements with Bulgaria, Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, Slovakia and Slovenia. The provisions of these agreements allow for the transfer of key personnel between a parent company in the Europe agreement country and a UK based subsidiary and are encompassed within this category.
http://www.workingintheuk.gov.uk/workin ... _send.html?