Vodafone Group plc slid on Monday after UBS downgraded the shares to 'sell' from 'neutral' saying it sees three potential risks.
The bank said Vodafone has made significant progress in reshaping its portfolio, returning cash to shareholders and turning around Vodafone Germany.
"However, with the shares up 34% year-to-date, Vodafone is trading on a valuation premium to peers and we think material risks have been overlooked," said UBS.
Firstly, it pointed to rising competition in German Multiple Dwelling Units.
Secondly, it noted a de-rating in Vantage Towers from the loss of Spanish revenues and thirdly, it pointed to the potential loss of the 1&1 NRA should there be German mobile consolidation.
The 1&1 NRA refers to a national roaming agreement (NRA) between Vodafone Germany and 1&1 Mobilfunk GmbH in Germany.
UBS nudged the price target up to 80p from 72p.
At 1410 GMT, the shares were down 3.1% at 89.28p.