The deal comes just a month after French tycoon Xavier Niel agreed a 2.7 billion euro (£2.4 billion) deal to sell mobile towers in France, Italy and Switzerland to the Spanish phone towers company.

The agreement with BT is worth around 100 million pounds, and includes a commitment to explore further opportunities between the two companies in Britain, Cellnex said in a statement.

Cellnex is Europe's largest phone towers group and has bought tens of thousands of tower sites in Europe in the past three years.

The telecom company is expected to acquire more towers this year and next, with focus on Western Europe and Britain, CEO Tobias Martinez told Reuters.

Shares in Cellnex were up 1.5% in early trade, outperforming Spain's leading market, the Ibex, up 0.22%.

(Reporting by Paul Day, editing by Louise Heavens)